Our trip this summer took us to KOA West Yellowstone. This is a great place for a family. Only six miles from the West entrance of the park, indoor heated pool and spa, lots of KOA family friendly activities, snack shack and restaurant, lovely tree covered park, level spot, just a real nice place. At the Tetons try to find time for the Bar-J Chuckwagon Dinner and Show in Jackson. A truly entertaining family evening, and the food was good too. Excellent cowboy music and stories. There is a zip-line at the ski resort in the town of Jackson, (not for me but the grandkids had a great time). Have a wonderful time, make memories, and Happy Trails.
PS: If you have any problems around Yellowstone, or need to rent anything I highly recommend Big Sky Rentals in West Yellowstone. My Adventurer motorhome need a engine air conditioner something or another, and I was told by many not to drive any distance for it could cause the belt to break and freeze the engine. Big Sky diagnosed the problem and ordered the parts, put me back together so I could return to the RV park in the evening after touring all day, then had me bring it in the following day for the repairs, again while we spent the day touring. Totally saved the vacation. We rented a 12 passenger van from them also, so that our whole group (3 families) could tour together. Good People.