#1 - and this is JMHO, don't stay in Pigeon Forge - Stay in Townsend you are still 20-ish min from all the action in Dollywood, et al but you are two-million miles away from all the hectic crowded craziness. Wake up in the morning to a whip-o-rill and the sound of trout feeding on the surface of the river instead of cars, trucks, and late night party animals swearing off drink for the tenth time
Tubing down the river in Townsend will be the highlight of the boys trip - I know our kids loved this!! (you go down the river in a tube, they pick you up, rinse repeat all day for @ $25/head)
White Water Rafting - a GOTTA DO - the boys will love it. Our kids enjoyed the Dollywood Water Park more than Dollywood but we have mutant seals for kids )or DID - they are 22 & 18 now
Gatlinburg is fun, the themed dinner shows are good entertainment.
#2 KY...LOTS to see: The Corvette Museum in Bowling Green, Mammouth Cave (Take the historical tour and unless you are 300+ lbs or in a walker do not let them frighten you off from it being too physical - it is NOT!) The boys will LOVE it. They have other cave tours specifically tailored for kids as well.
With boys that age they will KILL you if you do not take them to the Dinosaurs (don't worry, you CAN'T miss the Dinosaurs LOL).
Fort Knox is up the road and the Patton Museum is neat with tanks and all. Of course you can see Ft Knox gold depository (from a distance
Abraham Lincoln's boyhood cabin is preserved and you can visit that as well. There is a large Amish community in upper KY so you can go shop there and get some amazing fresh produce, meats, cheeses, jams and honey!
If you are so inclined, and the boys like Baseball, Louisville is home to the Louisville Slugger factory. You can tour the factory and watch them make bats - and not just production bats but custom bats for the major League Ball Players! You can also have a souvenir bat made with their name engraved and burned on the bat (as I recall the price was not unreasonable).
Of course in Louisville you have Churchill downs race trace, and the chance to take a paddlewheel boat ride on the Ohio River
In KY, I would stay at Singing Hills CG in Cave City KY. It is a Passport America CG and the owners are as nice as can be, sell firewood without scalping you & propane is dirt cheap as well. They have a catch and release pond that is private so you do not need a KY fishing license!
Believe i or not, you could base from Singing Hills and do all this - Bowling Green is @ 30-45 min South and Louisville is @ 1 hour North - well worth it for the quiet peaceful CG at Singing Hills...
If you decide to relocate to see all the sights around Louisville, HIGHLY recommend Glendale Campground. Right off I65 in Elizabethtown - which will put you 25-ish min from the Patton museum, Ft Knox & Louisville ( it is about 35-ish min North of Singing Hills