Here's the official Yellowstone site and it has a good list of things to do:
Yellowstone Nat'l ParkGrand Teton has a similar site, as do all the national parks.
Grand Teton Nat'l ParkColter Bay RV has the full hookups. The campground is right next door - no hookups but nice.
Personally, we like Gros Ventre campground (no hookups) the best. It has beautiful views is close to nice hiking, has animals cruising through and is closer to Jackson for doing things there, including major groceries just south of town.
Definitely take a gentle float trip down the Snake River in the Tetons. You just might see a moose in the water along with you! We did.