Need stop from NH to Sevierville, TN

The first week of August we'll be traveling from Portsmouth, NH to the KOA in Sevierville, TN with 3 of our Grandkids. We'll be going down 81 and stopping overnight half way. We had planned to stop at Yogi Bears in Hagerstown. But we stopped there on our way north and the line in April to check in was way too long so looking for alternatives.

I would consider a CG close to 81 without hookups, but we have a 45' MH and are towing a truck. Would also consider Walmart's, rest areas or anywhere safe. We are self contained. Boondocking is fun.

Any thoughts??