We stayed at the KOA in Townsend. http://koa.com/campgrounds/townsend-great-smokies/
Less crowded than the Gatlinburg area. At the Townsend KOA, my kids enjoyed the pool and tubing down a river/stream that is adjacent to the campground (water level varies with seasons). When we were there, water level for tubing was about 3-4 ft, just deep enough to go tubing (fun!), because is rained the previous day. After a day of sightseeing and no rain, the river/stream was not deep enough for tubing. Most sites are shaded and have adequate spacing. There are sites on the riverbank but some of those can be tight depending upon the size of your rig. Overall, a nice KOA.
2004 Suburban 2500 LT 8.1L/4.10/4x4
Putnam XDR Class V, Equalizer 1400#
2006 Jayco Eagle 264BHS
Iota DLS-55, Progressive Industries EMS-HW30C, Trimetric TM-2025