We are going to Mt Rushmore. Initially we were going to also go to Yellowstone but we don't think we have enough days planned to do both Mt Rushmore and Yellowstone. We have decided to go South and hit Colorado and then thru Kansas on the way home. Any must sees on I70
I can point you to some fantastic BBQ places in KC. KC also has some great stuff....Schlitterbahn water park, Nascar track, Worlds of Fun, etc that is worth a stop on the way home.