I didn't mention this in my earlier post, but how about the Pigeon Forge/Gatlinburg area? That should be within your 6 hour limit. I think it'll take about 5 hours, according to which part of L'ville you are in.
It has plenty to do, both outdoorsy and commercial stuff. Dollywood will be open by then, they usually open first couple weeks of March. Weather may or may not be good, but usually it's at least 50ish during the day and maybe 30s at night. There are many, many campgrounds there with different activities available. Our favorite is Pine Mountain RV Park. It is a bit pricey, but it has indoor and outdoor pools, a lazy river pool and a huge hot tub. Wonderful individual shower rooms if you don't want to use yours. It's right in the middle of the action, but is off of the bypass so you don't get all the noise. It gets great reviews and they are well-deserved.