You know the more that I think about your planed trip that with all the “NEW/DIFFERENT/CUSTOMS/LAWS” etc and the DISTANCES between MAJOR attractions that for the first time you should limit your trip to only two major destinations and then use two Airline arrival/departure locations. Then rent a Air B@B, bed and Breakfast close to your major destinations.
Example- Fly into LAX or Salt Lake City, UT rent a car there and drive to West Yellowstone, MT (6-7 hr including lunch from SLC, add 9-10 hr from LAX) stay in a Air B&B, stay there 3-4 days, then drive to Jackson, WY to a Air B&B, stay there 3-4 days then drive to Grand Canyon, AZ to a Air B&B ( in Williams, AZ) for 2-3 days the return the car to Phoenix, AZ and fly out of there to return to Italy. That way with everything NEW in the US you would not have to worry about a RV. Remember that between getting up in the AM, packing, feeding baby, 6-8 hours driving, checking in, eating, un-packing will wind up taking a FULL day.
Now about a RV- They are just like a Hospital, absolutely no privacy and ALL modesty is out the window, especially for younger couples that want THEIR private personal time! Then you know about infants they require their “own” private personal time. Then there is the going to a un- familiar grocery store, shopping for un- familiar items going back to the RV and figuring out WHERE/HOW to store everything. How to dump the waste Tanks, fill with water, how do I level/stabilize it, are you sure that I can BACK this thing into THAT space! (this is after a 6 hour driving time turned into a 10 hour day after a flat tire)
Also in Y’Stone/Tetons when going from one thermal attraction to another PARKING the RV is another problem.
