My recommendation would be the Colter Bay campground. It is centrally located in the park and close to the very interesting visitors center, Jackson Lake, Jackson Lake Lodge, and the highlight of the park, Oxbow Bend. Every night near sunset Oxbow turns into a zoo without bars because it is the only convenient watering hole for miles. Since it is an oxbow the water moves very slowly compared to the rest of the Snake River. There are a few beavers that are a blast to watch. There is also elk, pelicans, moose, bears, wolves, river otters, bald eagles, and tourists hanging around. Get there by 6pm to insure a good parking spot.