Have a wonderful first trip! Two apps we use the most are Allstays Camp & RV for campgrounds,and Gas Buddy for good fuel prices.
One thing I didn't know beforehand and have learned is to not over-schedule. You need to allow time in a schedule for days to just relax, clean the RV, do laundry, get groceries, and deal with inevitable little - or big - repairs or family needs.
Another thing I've learned is to plan 300 - 400 max miles driving per day and take plenty of breaks. Driving hundreds of miles every day for weeks is exhausting. If you get off the road by 3 p.m. You can park with daylight, build a campfire, relax, walk around and maybe swim in a campground pool (I don't agree that most of your nights should be in WalMart parking lots.)
If your trip is five weeks to include a week with family in CO, that leaves a month. If you are driving back home from the Pacific NW to Florida, that's 3000 miles at the end, a week of non-stop driving days. So that leaves three weeks free to cover many miles in the heat of the summer. Yellowstone alone needs at least five days. It kind of sounds overly ambitious and exhausting to me, to be honest.
An alternate itinerary suggestion since you are in Colorado already is to spend more time in that fabulous state. RMNP, Colorado National Monument, mountain towns like Ouray, Durango railroad, Mesa Verde, and much more. Then work your back back home, breaking up the trip at other interesting places.
