Nelson

Sounds like you are really doing your homework.

It's the classic American West conundrum of visiting both the high mountains and the red rocks country on the same trip without running into winter weather on the one hand or scorching heat on the other. It's 100% possible but it takes some planning and compromises based on your interests, budget, and the amount of time you have. I think you'll arrive at a good solution, but here are a couple ideas:

A route including RMNP
https://maps.app.goo.gl/UhT874UdVAKGGCLaA

Without RMNP, it knocks about four hours in Google drive time off the route. (Google drive time should be padded by maybe 25%.)
https://maps.app.goo.gl/jTjMGE6RarqqorhDA

You can play around with those and see what happens, you probably already are.
In general you "should" be able to alter hotel plans at short notice in October, except for stays inside National Parks like Mesa Verde or Zion.

Does a photo like this pique your husband's interest?? A typical day in Utah canyon country.



Have a great trip!

tomfuller

OK, fly to Denver and spend a night there. The light rail from the airport takes you to Union Station(Amtrak station). After a day or two in Denver, take the westbound California Zephyr shortly after 8AM. About 2 PM you will arrive in Glenwood Springs. The world's largest hot spring fed swimming pool is in Glenwood Springs. Just before getting into Glenwood Springs you will go through the Glenwood Canyon. Riding through it on the train is a lot nicer than driving through it on I-70 IMO.
Go west on the train from Glenwood Springs to SLC and rent whichever vehicle you want to go to the southern Utah National Parks. The bad thing about the CZ coming into SLC is that it arrives late night or early morning. Arriving by train in SLC I've taken a taxi to the 24 hour Denny's to hang out until the car rental place opened at the airport.
My wife and I took an anniversary trip to Arches and Canyonlands in early November one year and the weather was beautiful for the whole week in southern Utah. About 20 miles north of Moab (Copper Ridge) is a place where you can see a dinosaur track in stone. In Price Utah, there is a good pre-history museum with some dinosaur stuff.

StantonHyde

If you click on my user name you will find trip reports for all of the Utah 5, Dinosaur NP, Yellowstone, and Grand Tetons--all with kids. So very much written from a standpoint of having young people who need to get out and get going vs. long car trips all day.

You will need to think about weather with these trips--April or October is great for the Utah 5. I personally prefer the spring because flowers are in bloom. You couldn't pay me to go to those place in August--andi it's monsoon season so that means flash floods, not good. You can't really go--or won't want to go to Yellowstone and others in April. If you could do your trip at the end of September/beginning of October and start up north and then work your way down south, that would work well.

I live in Salt Lake City and this is what I would do--
1. Fly into SLC and drive up to Yellowstone taking the scenic route if your husband wants amazing scenery. Or take the route I mention in my trip reports and make stops in Blackfoot to see the Potato Museum (I am not kidding!!!) and the museum in Idaho Falls is good for a break. It's 6 hours to West Yellowstone. Stay overnight and then start Yellowstone. See my trip report and your own research to figure out how long you want to stay.
2. Go to the Tetons--stay in Jackson or the cabins at Moose that I mention in my trip report.
3. Drive back to SLC, stay overnight. Start the morning with a visit to the Natural History Museum which is truly incredible and has amazing dinosaur stuff!!! (I would skip Dinosaur NM but see my trip report on that too)
4. Go to Moab--see the Mill Creek Dinsosaur trail and all of the other amazing stuff in Arches and Canyonlands
5. Head over to Capital Reef--make sure to stop at Goblin Valley (a little out of the way but totally worth it)
6. Then make the AMAZING drive to Boulder/Escalante--but check the road closure over Boulder mountain
7. I would stay a night in Escalante so you can do Peekaboo and Spooky slot canyons--see trip report
8. then go to Bryce
9. Zion
10. Close out with the GC- and fly out of Vegas

Gretchen

DO take the scenic route from SLC to Jackson Hole. I thought it was maybe the most beautiful part of an extensive trip west we took. Jordan Canyon.

Patty

Logan Canyon (not Jordan) is beautiful particularly if you hit the fall color.