Man, what a bunch of doom sayers. If RV travel was as tough as some here make out, there wouldn't be a Forum of thousands that enjoy it. I think some of your assumptions will quickly fade once the travel in the Motorhome begins. The motion on the road of a 40' long bus is a lot different than car motion sickness. I'd bet the kid is going to be so pumped up about the trip, he'll fare without any sickness at all. Also, I've been treated for Lyme disease and the antibiotic is mild. Maybe bring along a six pack of yogurt to replenish the patient's GI tract, if needed.
What I'd suggest for the first day is to rent a few movies, maybe "RV" with Robin Williams so the trip gets off to a good, happy start. I've travelled with youngsters and the best thing is to keep them from getting bored, as you probably know. If you have some specific venues to visit, maybe some videos or printed material about that destination would be a good thing to have.
About Chattanooga--That tram looks like a great activity, I wouldn't avoid it at all. Actually, Tennessee is a beautiful place, lot's of things to see and do.
Happy trails and do let us know of any rabid monkey spotting, lol.
