States vary in rest area policies. Many post no overnight camping and some have rather short maximum stay limits (four hours, for example). Whether sleeping in a parked motorhome counts as "parking" or "camping" might vary with the exact wording of the law and/or the mood of any police officers; certainly things like putting out the awning, building a campfire, etc. are not recommended. (On the other hand, one of the reasons for having a safety rest area is to permit tired drivers to take a rest so they can drive safely.)
For the trip back, you might want to think about going along the Blue ridge parkway/skyline drive. Beautiful scenery, and while there is certainly mountain driving, it's not too difficult in that the speed limits are relatively low and everybody goes somewhat slowly...and there are many places to pull off and stretch and let people go by.
