I'm editing this to make sense...it was jumbled as I first typed...
Mama:
Take a tent with you and camp....are you going to Rapid City or Billings Montana? If you go in Rapid - you can hit Mount Rushmore first...then Custer State Park. Mount Rushmore is fun - there's an exhibit about the carving of the tower, history etc. You walk up and there is a state flag for every state in our union!
Spearfish, South Dakota: There is Spearfish Canyon (Bridal Veil Falls). It's a BEAUTIFUL drive...there's several campgrounds in Spearfish - and the fishin' is good!! After that - I would then head west on Interstate 90, towards Sundance/Moorecroft, Wyoming...then take the exit 185 (Hwy 114) for the Devils Tower..then explore the Black Hills....The Devil's Tower is the First National Monument of the U.S.. If you have seen the movie "Close Encounters of the 3rd Kind" that's where the aliens landed...
About the Devil's Tower National Monument - it is in the North East corner of Wyoming. You can walk around the Tower - there are two paved paths, you can climb up to a certain point...and if you are a climber - you can check in at the Ranger Station and climb to the top! Its about the size of a football field up there. It's a great trip!! there is a campground at the base of the Tower (okay, not the base, but there's a National Campground in the park....and a KOA right across the gate to the park...as well as a "trading post" that serves AWESOME ice cream and a ton of stuff...camping supplies, etc.
http://www.nps.gov/deto/index.htm
Continental Divide driving tour
Yellowstone
If you want to make the long haul? Jackson Hole - south west corner of Wyoming....a LONG days' drive...
Then there's Glacier National Park...wait is it a National Park? Either way? VERY NICE!!
Contact AAA and ask them to map out a drive for you - they will give you lodging as well as other things to do....