WOW! Thanks to all, for all the great tips and thoughts.
I know this trip is pretty aggressive. I was planning to be aggressive on the first part of the trip, to get to Rapid City. Then start the site seeing. Mt. Rushmore, Crazy Horse, Devils Tower, Little Bighorn and Yellowstone. Not all sites on the way west. We are going to stop at one or two of these on the way back east, after stopping in Missoula. Then back to aggressive pace on the return trip.
My wife is a pharmacist and the chances of taking off for 3 weeks is very slim to none. She is going to try to gather up a couple of "personal days" tacked on. We'll see.
I'm self-employed and a stay-at-home dad, so I have more flexibility. Worst case, if time runs out, my wife said she could fly back to Baltimore BWI.
Once again, thanks to all we really appreciated all the info.
2016 Sonic 220 VBH 26ft./Ford Explorer