I haven't made it to Yellowstone or the Tetons but have had several friends make that trip. Yellowstone is a big draw for them but the Tetons, not so much. A day or two in the Tetons were about right for all of them. Spend more time in Yellowstone was the advice I received.
I have, however, been to Mount Rushmore and the Black Hills several times. You can do Mount Rushmore in a day but you'll want to take a car IMO. I think you'll want to come back on a second trip because there is so much to see and do in that area. It's not just Rushmore. It's caving, the alpine slide, Custer State Park, Crazy Horse, the Black Hills and so much more. If you have time, definitely stop by the Badlands. You'll really want a day to spend there if you decide to stop. Just beautiful.
Just my two cents' worth. I hope y'all enjoy your trip!
