Japan

Kyoto for sure. Much more “approachable” than Tokyo.

Oh golly - the choices are endless! Is "next fall" 2023 or 2024? How long? Lots of fun research ahead!

Tokyo - as you note, much to see.

Take a look at Kyoto - historic city. Temples, shrines, some tourist-oriented experiences like tea ceremonies, I think some Samurai type places aimed at kids, easy day trips. The Arashiyama area outside Kyoto has a monkey park, interesting temples and streets to wander, bamboo forest, river boat, other enticements. From Kyoto easy to get to Nara with free roaming tame deer and unique, historic temples, hiking. Himeji Castle is easily done as a day trip. Fushimi Inari - hiking and temple.

Osaka for the aquarium and Universal Studios and a couple other kiddie amusement parks. Himeji Castle is easily done as a day trip from Osaka as well as Kyoto.

Osaka or Kyoto can be used as a base to visit either city. Trains are many.

Hakone - a volcanic area between Tokyo and Kyoto. Some do this as a day trip from Tokyo. Train, cable car, ski lift that is called a Ropeway over a volcanic area. Hiking, museums, look at the Open Air Museum for kids if you are interested in the area. A day trip is possible, but a long day of mostly covering ground on the transport route. Hot springs baths.

Japan is quite easy to DIY. Some of the train stations are huge - follow the English language signs and perhaps examine maps before you go and you will be fine. The train system is incredible and easy to use.

There are some very fine websites with good info. Try these:
https://www.insidekyoto.com
https://www.japan-guide.com
TripAdvisor forums are very helpful with some excellent, detailed advice and instructions from several generous expert posters.

I forgot to mention Miyajima Island that is near Hiroshima. There are interesting sites in Hiroshima other than the Peace Memorial if you think that would be too much for your children. While very moving to many adults and older kids, I (personally) would examine that closely before taking young children.

Depending on your interests, near Matsumoto there is Jigokudani Monkey Park. That area is near the Japanese "Alpine Route" if it fits your interests. Castle in Matsumoto.

Hakone provides some views of Mt Fuji. There is another Fuji area - Fuji Five Lake - region that you could research. That is also sometimes done as a day trip from Tokyo.

I'd comment that Tokyo is very easy for English speakers, if you like a big-city experience. I don't mean that people speak English, but that the subway stops have numbers as well as Japanese names. Osaka is also easy to tour without knowing Japanese. Kyoto is a special case of smaller city, but I think the beauty of the temples, and the views and gardens of the bigger temples will interest children.

Check dates for Chrysanthemum festivals.

EDIT: Some Japan Rail offers may be available only for advance purchase while still in the USA. Local Japanese offices of Japan Rail were very helpful when we arrived with advance coupons.

We loved Japan, spending 6 days in Tokyo.
We did a day trip to Nikko north of the city. It is amazing, famous for the 400 year old cedar trees.

Kamakura is south of the city and we did a day trip there. The giant Buddha is amazing.

Kyoto is NOT to be missed. We did a three day tour from Tokyo that included a half day tour of Nara and two full days in Kyoto. The tour included RT on the high speed train. If you go to Kyoto, be sure to take a tour that includes the KEY shrines and temples. There so many that you can't see them all. Be sure to see the Golden Pavilion and Silver Pavilion. Also, the Philosopher's Walk that includes several shrines and temples.

After coming back to Tokyo, we took a cruise that ended in Hong Kong, that was great. We stopped in Kobe, and visited Osaka Castle that was great. Another great place to see was Himeji. Also, we visited Nagasaki and Okinawa.

If we are getting into specific temple recommendations, I'm going to give you mine! For background, I lived in SE Asia for multiple years and am very familiar with the Buddhism and temples of Thailand, China, and Cambodia. Japanese Buddhism is a variation and reflected in many of the temples. Shinto Shrines are different from Buddhist Temples.

My personal favorite temple in Kyoto is Sanjusangendo. https://www.japan-guide.com/e/e3900.html It is not always included on tours, but it is quite different from many of the Zen temples and temples of other sects. With 1001 life-sized statues, I think it might hold the interest of younger kids better than some of the simpler Zen temples or Shinto shrines. It is fairly close to Kiyomizudera Temple, a temple often cited as a traveler favorite and again, one that might appeal to kids because of its location on the mountainside. https://www.japan-guide.com/e/e3901.html

It is quite easy to walk between temple and shrines in the Higashiyama and Gion Districts. I would definitely visit that region - preserved streets, restaurants, tea houses (unique Starbucks!), street food, tourists dressed in geisha costumes from the many rental shops. With short time, I would recommend this area over the Philosopher's Path area. However, there are many small temples and shrines off the Philospoher's Path that might appeal. Kinkakuji (Golden Pavilion) is an impressive sight, but not close to other areas that are highly walkable. Consider a taxi if you visit - there is a taxi stand outside. It also gets very, very crowded.

I have always done a DIY tour of temples. A guided tour would probably be useful if temples and shrines are new to you. However, I am not certain that 2 8-year olds will be as interested in hearing about sites as simply exploring. I found these maps very good for planning https://traditionalkyoto.com//wp-content/uploads/2017/05/Kyoto-Walks.pdf

No one has mentioned Nijo Castle in Kyoto or Nishiki Market. You might consider those. If you visit Nishiki, I advise going very early. It can get very, very crowded and easy to loose travel companions.

If you end up in Kyoto near the Philosopher's Path, the Otoyo-jinja Shrine with its mice statues might especially appeal to kids . Scroll down to find the pictures and descriptions https://www.insidekyoto.com/walking-the-path-of-philosophy. Similarly, if the adults are interested in Fushimi Inari, you might try selling it to kids by asking them to count the number of fox statues you can find at the shrine. https://www.japan-guide.com/e/e3915.html

I'm headed back to Japan in October. You have me started on review and revision of my plans. No Kyoto this trip, sadly.

Check out my trip report--I visited Japan in Mar 2023. If your kids like Sanrio Characters (Hello Kitty), then take a commuter train from Tokyo to enjoy Sanrio Puroland indoor theme park.

I am returning in Nov 2023 and Feb 2024!

Thanks all. This is amazing! I going to go through all your comments. We are planning to Fall 2024z

Another thought for Tokyo that often doesn't pop up easily in searches and is not particularly well-known. The Nihon Minkaen Open Air Museum of historic buildings from various regions of Japan. You can walk into the buildings which might be fun for the kids depending on their interests. A samurai's house, farmhouses, etc. Everything is in a park setting. There is a science museum that is geared to kids just steps away from the Open Air Museum. Short, easy train ride from Tokyo, then about a 15 minute easy walk on sidewalks to the park (or taxi). https://www.japan-guide.com/e/e3253.html

ORDtraveler,
Yes, we visited Sanjusangendo temple and it was amazing.

Hooray, geovagriffith!

I always want to spread the word on Sanjusangendo. Because it is just slightly set apart from obvious temple routes, it gets skipped or not suggested for travelers short on time. There is a taxi rank!! and it is less isolated than Kinkaku-ji.

I almost skipped it myself since it didn't appear in the "temple itineraries" that I found online when planning. What a treasure I would have missed!

OP - another thought on transport within Kyoto. The subway system is somewhat limited. It is good for the areas it serves, but isn't like a full London Tube system or a Chicago or NYC style get the commuters around the city set-up.

If you plan Kyoto sites, you might have transport in mind. There are buses, but they get very crowded and are quite slow. I would avoid these except perhaps early AM or very short distances. I took a number of taxis. These can also be slow depending on traffic, but was often the best way for me to get from point to point. The trains to outlying areas such as Arashiyama, Fushimi Inari, Nara, Osaka, Himeji Castle are excellent with lots of choices and no need to book in advance (unless you choose to do so). The above walking maps include major areas of Kyoto. Walks are easy, sidewalks, some hills but nothing steep, interesting, safe to wander. If you get to the areas of interest, no problems walking around with the districts.

Tokyo subway and train system is very good. To efficiently follow signs in the large station, you do need to understand if you are looking for a Metro line, a Toei Subway, or a train line. This is a good intro https://trulytokyo.com/tokyo-subways-and-trains/
The transit cards make usage quite easy - check the rules for kids, probably a discount or free ride. Taxis are also readily available in Tokyo. With a family, I wouldn't rule that out.

There are also apps to help plan transit - both within cities and inter-city. Search Navitime and Jorudan. The apps will even tell you what platform you need at stations and which car is closest to your destination. I use these both in planning and when on the ground - invaluable!

Everything ORDTraveler has said.

Kyoto for sure - beautiful, and what most people think of when they think of Japan. Hakone for varied and eclectic (and kid-friendly) stuff like sulphur vents, black eggs, cable car ride, pirate ship on the lake, hot springs. Might be fun to find a traditional ryoken there (hotel) for an "authentic" experience, sleeping on tatami mats, dining in kimono, etc.

I would also add the Ghibli Museum (Tokyo) if the kids are into anime and familiar with the Ghibli films - Spirited Away, Kiki's Delivery Service, My Neighbor Totoro, Howl's Moving Castle etc. https://www.ghibli-museum.jp/en/. It was not open yet when we were there in 2017 and my adult "kids" would have loved to go there. Big Miyazaki film fans.

I've been to Japan 5 times or so (I lived in Korea for several years) and absolutely hated Tokyo the first time I visited. It was so massive and overwhelming. Each time I've been back, I've liked it more. The trick for me has been to stay in a more local neighborhood and discover it a neighborhood at a time. With that being said, Kyoto is more accessible and has SO much to see. You could stay for a week and not scratch the surface.

Places I especially love are Nikko (if you like temples and outdoors, cute towns), Takayama (gorgeous historic central, wonderful outdoor museum nearby), and Hiroshima (local feel with visit to nearby Miyajima).

A couple of people have mentioned Tokyo being overwhelming and hard to approach. I find that a very curious and interesting narrative. Yes, Tokyo is large but you don't have to take it all in at once and there's no point in trying to try to do it all. Instead of being "greedy", just approach it a little at a time. Do some research on what is available to do and make up an itinerary.

I found the signage pretty navigable.

When I visited Japan, we had one week and we did visit Tokyo, Hiroshima, Miyajima, Kyoto etc. It was a lot and a lot of fun. You don't have to do all those places. One thing I definitely wanted to do was ride a bullet train which we go to do so travelling from Tokyo to, I think it was Hiroshima. If you and your family are interested in riding the bullet train, you might consider what attraction away from Tokyo would mean taking a bullet train. I thought it was quite enjoyable to ride the train and eat bento box for lunch. A lovely experience.

Our visit to Japan was in 1987, so some of the detaills are a little fuzzy in my mind. However, one thing that struck me was how child-friendly it was. Several of the sites, museums and castles, had costumes for children to dress in. There was a toy museum in one town. I’ll try to find the name and post it for you. Interesting for adults, too. There are towns that have craft centers where you can participate in a local specialty. We did paper-making, indigo dying, pottery glazing, and origami.

Not a popular opinion, but Nagoya is a great place to visit. I would recommend renting a car so that you can maximize your stay here. I believe Nagoya is underrated :D