Family of five first time to Croatia itinerary support

How exciting for your family!
I think that your pacing looks good. I would do 2 nights Split.

How old are your children? Their ages might determine the advice people give.

Three nights is good for Dubrovnik. You might want to consider a day trip around the Bay of Kotor in Montenegro, instead of Lokrum, while staying in Dubrovnik. That's up to you. Just want to mention it as an alternative.

I would definitely spend 2 nights in Split. It's a beautiful city. We hired Maja Benzon, recommended by Rick, as a tour guide for a private 2-hour tour of the Old Town and Diocletian's Palace. The Ethnographic Museum is very interesting.

While at Plitvice, we stayed at the Plitvice Miric Inn instead of the over-priced park hotels. It's 5 minutes from Entrance 2. Our cost in 2019 was 130 euros which included a magnificent home-made breakfast buffet. They also serve an amazing dinner for 20 euros per person. You will have to buy 2 tickets for the park, however, but we thought it was worth it.

Thank you. Our children are 16, 14, and 12. I will look at the Bay of Kotor as an alternative. Thanks for all the tips on the park/ hotel etc.
Has anyone rented a car in Split and dropped off in Rovinj?
What is the best transportation mode from Rovinj to Slovenia?
Would you split staying two nights on Korcula and two nights in Vis? Or stick with one island?
Thanks again!!

Split has an unusual feature - a fine sandy beach. Your kids might enjoy that.

There's also the archeological museum.

Trogir is a full day. I don't know if you want to spend that much time on it. It's a great town, but Split is also great. Take the "Split Plumbing" Tour - you go to the basement of the palace, and see how the mechanics worked.

There are also the Roman ruins outside of Split. I'd go there.

Are the kids doing research? I'd get them going on Diocletian and the Time of the 4 Emperors.

You should have no issue renting the car in Split and dropping in Rovinj, but check with a few rental agencies as prices have been higher recently.
I would not go to Vis for fewer than three nights because of the longer ferry time, so I’d choose one island. That way you have time for hiking, biking, boat excursions, that kind of thing.
What’s the plan for Istria? Partly it’s that I haven’t spent time there and have in Dalmatia, but you could focus more on Dalmatia, and end in Zagreb after Plitvice for a train to Ljubljana.
You can definitely do outdoor things in Istria too, it is just that there is a lot of talk of driving among hill towns in Istria, so I’d be thinking of what the kids will enjoy.

I liked Istria. Rovinj has a medieval core. Porec has brightly-painted houses. Pula has some Roman ruins (which I haven't seen). The hilltop village of Vrsar (between Rovinj and Porec) is cute. And you have the rural interior with old villages like Motovun and Groznjan. At the time of my 2015 visit, there was a zip line near Pazin. Google's telling me it's closed at the moment, but I imagine that's just for the winter.

If you take the (magnificent) Bay of Kotor side trip, Herceg-Novi is worth a stop.

Thank you to everyone! Your feedback is very helpful. I’ll be back after booking some accommodations and activities with additional questions. What a great forum.

Sounds like a fun trip! We visited Slovenia and Croatia last summer and had a great time. We found public transportation between Croatia and Slovenia to be tricky, so we rented a car.

Another thought is to keep the car after Rovinj to drive to Zagreb and drop it there. It’s only a 3 hr drive. Then catch public transportation to Ljubljana. I used a local company called UniRent and they have offices in both Split and Zagreb. My car was great, as was service, and it was quite a bit cheaper than one of the major companies. They do one-way rentals.

Your pacing looks well-thought out. Yes for 2 nights in Split. I haven’t been to Vis so can’t answer, but I did love Korcula.

Thank you for your tips on rental car and Zagreb. I will take a look at the rental car company. I appreciate all of these ideas from seasoned travelers.
Dubrovnik: we arrive at 6 pm. Between jet lag and settling in that night, would you recommend three full days there? That would be Weds- Friday, check out Saturday? I was planning on two full days/ three nights but not sure that’s enough time. Also all the RS recommendations are booked, obviously. Is staying in the old city walls the most ideal way to visit? We live in Southern California and are lucky to live close to the ocean. I noticed Ploce and Pile ( coastal) were nearby but also staying within the city walls is quite special. There are very limited rental options due to late booking.
Thank you!