I know there seems to be a lot of disdain for KOAs on this site, however, we enjoyed our time at the Jackson Hole/Snake River KOA. It is about 5 or 6 miles south of Jackson near the 191/89 hwy junction. The setting is awesome as it is right on the Snake River although the RV spots are up and away from being directly on the river. Very peaceful setting though. You can even get picked up at the front of the park for doing a rafting trip which is down stream a number of miles.
I actually brought my kayaks and put-in up the river a few miles and took-out right at the KOA. I would love to go back there some day.