Your advice is sound. 3-6 year old is good -- avoids most of the initial depreciation as well as the "needs major repairs" of an old unit. C class is also a good choice. I would add that the addition of a small car as a towed (aka "toad") might be useful, but perhaps equally useful instead might be an electric bicycle.
North America is a big, big place with a lot of unique things to see and do. May I suggest also a youtube channel called "Gone with the Wynns," by a couple who spent several years roaming North America by RV before switching to a catamaran and sailing the world. Their adventures will give you some good ideas.
