Rocky Mountain National Park 20+ Hr Road Trip

I went camping with young children. Always one parent needs to remain with a child. I had each one wear a whistle around their neck and I wore one too. If we got separated we would whistle three short repeats. The others whistled back.
Your son with sensory difficulties will need break times to get out of the car and just play.
When camping I always have vegan food so that bears and raccoons are not attracted to it. The lock up procedures for food are critical for everyones safety. I always carry bear mace with me when camping and I have used it on raccoons.

We did the trip to Denver and back twice by car and if I had it to do again I'd take three days. It is such a hard push. I had the kids sleep in the back of the car and drive at night part of the time. We stopped overnight after 11 pm.
The two best stops that were not in nature to and from Denver were Reno and Salt Lake City. We spent 6 hours in Salt Lake one day and it was very memorable.
My youngest daughter loved Wyoming. She had never seen desert before.

We drove from Texas to Rocky Mountain National Park with a one year old and a five year old. Drive early in the morning (really early!). If you have the time to break it up into three segments, that would be good. We have driven as much as 17 hours in a stretch (Des Moines, IA back to TX) but that was really long (and the kids were 4 and 6 weeks at the time. I would leave really early the first morning and try to get in 12 to 14 hours the first day. When you stop to eat, let the kids get out and run around. Books, games, DVD player and surprises from the dollar store are all good things on a road trip. That way you can do a lot less driving the next two days.
Rocky Mountain National Park is really pretty. We sent in the summer. A lot of the roads are closed in the winter. We drove all the way through, but did not stay in the park. We went to the Visitors Center (I don't remember which one) and hiked a little bit (very limited with a 1 year old). We go to Colorado about every other year and always love it. Have fun!

You didn't say what time of year you're coming to RMNP. Regardless, bring a good jacket just in case it snows, and yes, it can snow up there ANY time of year. If you go up Trail Ridge Road you'll definitely see snow.

Don't let the kids wander, keep hats on them if you're coming during tick season.

It's the mountains, everyone enjoys them!

We drove to Alaska with our almost-2 and 3 year olds in 2008. It was a 7000 mile trip. They did great! Of course I did a ton of pre-planning, had activities for them to do while in the car (every day for about 8 hours) and we took along their bikes/trike, balls, frisbees, bathing suits, etc to get the wiggles out when we parked at night or lunchtime. I got them trays for their carseats (soft trays in case of an accident), crafts like sewing cards, coloring books, magnetic 'paper' dolls, books, an MP3 player filled with books on cd from the library, we have satellite radio and the kid's channels are great (that was worth it's weight in gold).
The next year we drove down to Las Vegas and camped in the Sierras....they still had fun and are extremely used to going on trips and are very good travelers.
Have a great trip!

Could you fly and rent camping equipment?

That is a really long drive with two small children. If you drive, I would strongly suggest investing in a portable DVD player and tons of new (or gently used) books.

I would also suggest that you do at least a bulk of the driving during their normal sleep time. You and your husband and rotate who drives and who sleeps. If they typically sleep 8-10 hours at night you could cover a lot of the distance while they are rested then swap drivers.

I haven't made that specific trip, but do recommend getting portable travel trays. One Step Ahead has a really good, soft, collapsible one that we use for both kids. It's in blue, if you go to their site (this site won't let me post a link to it). Kids can color, read and eat on the tray, and there are pockets on the sides to store drink cups, snacks, crayons, etc. The trays have helped a lot for us on long car trips.

Best of luck on your trip!