Joe,
It seems to me that you have some serious decisions to make. I have been a lot of those ways and if I had to make up my mind for your route, I honestly do not know which I would do. I will say, that with a 3~4week schedule, it gets even harder.
First thought: Do Route 66. Get the guide book and pick up the mother road in Joliet. Where it actually used to start in Chicago is not someplace you really want to go. There is so much to see and do along the way that this is a monumental excursion.
Second thought: Half-Way between that could take you through Amana Colonies, Denver and Las Vegas. Again, get out the guide books and find out more.
Third option for this morning: A Northern Tier Tour that can take you to lots of interesting places. Do you even know about the Kensington Rune Stone? When last there, Mall of America was very RV-unfriendly but that may have changed, and if you have a towed, you might get into hiking range. Then there is the stuff east of Yellowstone. Crazy Horse, Rushmore, the Badlands and (of course) Wall Drug (a tourist trap with free cold water). The Buffalo Bill Museum And Yellowstone. Plan at least 3 Days in YNP (it takes that long just to drive the bigger roads).
This could go on for a few more pages. but I have other people to annoy today.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.