Early Planning Western US Tour

Make sure you book a Canyon Tour which takes you to the most important sites.

Have you considered Santa Fe? I was there a couple years ago and just loved it. If you like the artist Georgia O'Keefe her museum is there and her home & studio is about 50 miles from town.

I have traveled some in the region you are planning on visiting, but I don’t pretend to be any kind of expert. However, here are some thoughts and recommendations. The distances between sites can be daunting. Be sure to check in your planning. A one night stay does not equal a day. By the time you pack up, check out, and drive to your next destination, you might have no more than a couple of hours left for exploring.
I would include Santa Fe, and give it 3 full days. It has a wonderful museum of Folk Art and a Georgia O’Keefe Museum, as well as museums of New Mexico history and Indian Culture and art. The drive from Santa Fe to Taos isn’t bad, and you can visit the Taos pueblo there, as well as the Millicent Rogers Museum, which has a very good collection of indigenous art.
I have never heard of Tuba City; and I think Flagstaff is skippable, given all the other wonderful places to explore. I think 4 Corners is unremarkable. We eliminated it from our itinerary because it looked to be simply a marker noting the confluence of the 4 states.
I also don’t see any mention of the Grand Canyon, a top world-class sight. It’s worth visiting, even without any hiking. You can drive to several lookout points, and get astonishing views. We did it as a day trip a couple of times when we were hosting mobility-impaired visitors.

We did a similar trip last year. We flew into Phoenix, drove to Sedona and spent 3 nights (2days) here. In Sedona, you must do a Pink Jeep Tour.
We did go and stay in Flagstaff for a geocaching convention, but I'd skip it, if your time is limited. We did like going to the Lowell. Observatory in the evening in Flagstaff,
From Flagstaff, we drove North to Grand Canyon visiting the lesser known National parks of Wapitki and Sunset Crater. You can visit these in one day as you drive to Grand Canyon.
I see you did not mention Grand Canyon. So I assume you've already been here. If not, you need to stop here, even if just one night. We spent 3 nights.
We spent three nights in Page AZ, rather than Tuba city. We visited Antelope Slot Canyon and Horseshoe Bend.
From here we went NW, but you are going NE.
On the way South, consider Santa Fe NM and a Day trip to Taos NM via the High Road and then back to Santa Fe via the low road with a dinner stop at Rancho Chimayo. We also visited Santuario de Chimayo during our drive to Taos to see the Taos Pueblo. We spent 4 nights in Santa Fe (one of those days was a day trip to Taos and back) We are glad we didn't spend a night in Taos. Just to sleepy for us. Santa Fe has the Georgia O'Keefe Museum and great restaurants. I think September there is the Santa Fe Opera.
We also spent 2 nights in Abiquiu NM to visit the Georgia O'keefe home and Ghost Ranch and had a wonderful dinner at NOSA.
We stopped by Los Alamos, NM to see sites here, before heading to Bandolier NM.
Then we drove to Albuquerque. and visited Petroglyphs NM. We visited ABQ during the Balloon Fiesta, but it's not in September when you are going.

We did not do any heavy hiking. Hope these suggestions help. If you need hotel suggestions, let us know.

Please explain further:

1. Why are you skipping the Grand Canyon? Or are you thinking that Flagstaff would be your base to visit the Grand Canyon? If so, then that's a bad idea. If you are going to GC, then stay in the GC.

2. Why Tuba City? Again, your post is not clear when you mention visiting a list of other places in Arizona but not particularly close to Tuba City. Personally I would rather go from the Grand Canyon to Monument Valley and spend the night there. Take the Native American-led tour in MV.

3. Skip the tourist trap that is supposedly the Four Corners. Yes it's fun to think that you are standing in four states, but it's not even in the correct location.

NO GRAND CANYON!
Consider visiting some national parks, there are many in the SW. Utah has many in addition to the Grand Canyon. Also, visit the huge crater in northern central AZ.

Thank you everyone for your suggestions!

To clarify:
I did want to avoid long drives from place to place and I have been to the North Rim's Bright Angel Trail and hiked down to the Colorado River in Marble Canyon. DS hasn't been to the GC, but we have been to Iceland together. Neither of us can completely enjoy a huge chasm in the ground due to feeling vertiginous. I also dread the huge crowds. HOWEVER, I have decided to reconsider and am now thinking that we could go to the South Rim with a breakfast stop in Flagstaff.

The reason for Flagstaff is that I spent about 10 days there in my youth. When pre-retired folks in Ohio start talking about relocating to Florida, I always say I am moving to Flagstaff--nice high elevation where it doesn't get too hot. I am pretty sure I will stay put here in Ohio and keep traveling, but I would like to see Flagstaff again.

I have also stayed in Tuba City for a few days and would like to see it again. In addition, I read all of Tony Hillerman's books around this time and places like Shiprock, Pinon, Hard Rock and Gallup are stored in my brain. I love to visit places from TV shows, movies and books.

I now have Santa Fe on the must list. This will be the totally new place on the list to visit. Then we can fly home from Albuquerque.

Thanks for the help, the trip is shaping up much better!

We did two similar trips a few years back. I don't want to reiterate any of the above. However, I have a few more suggestions for stops we considered highlights. These are mostly museums as other highlights have been included above. They may not be of interest to you, but I'l link the relevant details.

Phoenix/Scottsdale (we also flew into Phoenix):
Musical Instrument Museum - this is not just for musicians or instrumental music enthusiasts. Very well curated and designed museum - will appeal to cultural, ethnological, world music, historical interests. Lots of hands-on, demos, audio guides, information available for intro or in depth levels of interest. https://mim.org

Desert Botanical Garden - fairly flat and easily walkable. We found it a good intro to local flora and topography.
https://dbg.org

Western Spirit Museum of the West - https://westernspirit.org

From Santa Fe, we drove to Los Alamos for a couple days. Manhattan Project sites and several other interesting spots such as Bandelier National Monument on this link: https://www.nps.gov/mapr/planyourvisit/losalamos-nm.htm

Also from Santa Fe, we did a day trip to Taos. Very attractive, but not rigorous drive. Taos, as an art colony, had lots of little spots to explore and enjoy.

Re the Grand Canyon - We enjoyed a couple days at the South Rim despite one of us not being able to hike. There is a flat, easily walkable path along the rim and shuttles for distance. I have a fear of heights, but managed this fine.

So much to see! Even after two separate visits, I have a list of sites we didn't manage to fit in.

I recommend Meteor Crater National Monument, about 35 miles east of flagstaff, about 5 miles off of interstate 40. Very cool, look it up. There’s a small museum and film and you can be in and out in 1-2 hours. Finally got there about a year ago.

vandrabrud,
We have done lots of road trips throughout the Southwest (coming from SoCal).

1. Don't miss Santa Fe. Fly into Albuquerque, rent a car there and drive to Santa Fe (about an hour). Stay at the Governor's Inn right near the Plaza. Lovely rooms, good food, neat bar, generous margaritas (popular with the locals)..... overall one of our favorite places we have stayed for comfort, service, ambience, location and value. Visit the museums on Museum Hill (there are four, but do not miss the International Folk Art Museum and the Museum of Indian Arts and Culture if you don't want to do all of them). On the way up or back stop at the Loretto Chapel to see its staircase. The Basilica Cathedral of St. Francis of Assisi, near the Santa Fe Plaza, is lovely.
IMO the Georgia O'Keefe Museum is disappointing.
Spend one day going to Taos. Take the high road one way and the low road the other. Visit the Pueblo of Taos. The town itself is a bit to artsy-craftsy for me and too commercial. On the high road route stop at Chimayo and check out the chapel. On the low road you drive right next to the Rio Grande (yes, that one). Another day trip could be Los Alamos to visit the Bradbury Science Museum (fascinating), and atomic history sights. Head back by way of Bandolier National Monument (cave dwellings).

All in all, three full days in Santa Fe is a minimum for me. Alburquerque is okay. It has the Indian Cultural Center and the Balloon Museum, both of which we enjoyed, but both can be seen in one day. Santa Fe has more to see and do IMO.

1. Arizona...Sedona is a a beautiful area. However, the town itself has become an upscale tourist enclave IMO. Find a scenic route to drive on yourself, or be judicious about which guided tour you take. Some of them drive up and back through town to point out the shops and give you a very short trip around the scenic areas (which are outside of town). Get a tourist type or AAA map and drive on the roads to see the beautiful rock formations yourself. To me, one day there is plenty as Sedona is so commercialized and overpriced. Just driving through town is slow due to all the traffic. Nearby Flagstaff, although not fancy, is in another setting altogether...mountain forests. The Lowell Observatory is worth a visit. Flagstaff is a college town so there are several reasonable places to eat.
   Canyon de Chelly and Monument Valley, both are fantastic! So glad you are going there. Canyon de Chelly is neglected, unreasonably so. You will be fascinated. And if you have time do go to Four Corners. Yes, it isn't much, but heck, it's fun to manage to put your feet in four states at once! Of course, the route to Four Corners is a bit out of the way if traveling between Monument Valley and Canyon de Chelly (about 3 1/2 hours between the two, and 3 1/2 hours from either place to Four Corners). The drive from Canyon de Chelly to Alburquerque takes about 3 1/2 hours also, and goes through Gallup NM. For some reason Gallup holds a special place in my heart. We stopped there between seeing Chaco Canyon (NM) and Canyon de Chelly. It is rich in Native American culture and arts, not pretentious, on old route 66. It could be a pleasant overnight stop. You may happen upon a powwow. (Stay in the historic Hotel El Rancho. We loved it, and the restaurant had delicious food.) Santa Fe is another hour past Alburquerque.
2. Re hiking. All these places are doable with bad knees (I saw them before my two knee replacements), except for climbing up to the cliff dwellings at Bandolier Natl. Monument. And Canyon de Chelly had some areas I didn't walk to, but the site is so large you won't cover everything anyway and may just drive on one of the routes with overlooks. Also, as far as dwellings go, Chaco Canyon has far, far more to explore. The two sites aren't really comparable, IMO. Each has its own strengths.
   
3. Tuba City...??

Lyndash has a good suggestion. Meteor Crater is very cool. If I remember correctly, early astronauts did some training within it.

vandrabrud,
No time for Phoenix this trip, I see. Next one......and add Tucson to that trip. Lots of stuff to tempt you on another Southwest trip.