Yellowstone is easy to get to from Billings. Just take I-90 west to Hwy 191 at Bozeman into West Yellowstone. There are no steep mountains to navigate.
When your ready to go to Grand Teton Nat'l Park (& you definitely should) you can either drive south through Yellowstone into Grand Teton or go back out to West Yellowstone and pick up Hwy 20 in Idaho to Idaho Falls, then take Hwy 26 into Alpine and Hwy 89 north into Jackson and Grand Teton. Again, no big hills.
In the Tetons, Colter Bay and Gros Ventre campgrounds (our favorite) don't take reservations and they rarely fill except on the 3-day holidays. Each one has 300 sites. There is also Colter Bay RV (which is next door to Colter Bay campground). The RV park has full hookups.
In Yellowstone, Fishing Bridge campground has full hookups and all the others are dry camping with water fill and dump stations. Madison campground is very nice and centrally located.
Here is Yellowstone's official park site for camping info, road info and what to do/see:
Yellowstone....and Grand Teton's official site:
Grand Teton Nat'l ParkHave a great trip!
