We can definitely agree that your first three choices are good ones. Here is a link to a couple of albums from Mt. Rushmore and Custer State Park
http://www.keystoneforums.com/forums...hp?albumid=775
and Grand Canyon
http://www.keystoneforums.com/forums...hp?albumid=851
If time permits, I'd recommend Grand Canyon, Zion Canyon, Bryce Canyon and Capitol Reef all in one trip. Don't forget Arches NP as an option as well.
If you decide on Yellowstone be sure to include a few days at Teton NP.
Feel free to PM me if you'd like more details.