Our family loves going down to the smokies too! Have you done Ober Gatlinburg yet? Its something that your kids would like as long as their not scared of heights. There's a ice skating rink, kinda like bob sledding, water slides, race cars and stuff. We liked doing the chair lift that takes you up even higher.
There is also a smaller cable car that takes you up the mountain at the beginning of gatlinburg that has putt putt on top of the mountain, its pretty neat.
I have done the helicopter tours. they are amazing. they range in prices from like $10 to $200. everyone who did the 10.00 tours said they where great and wanted to do a longer ride next time. i also have to agree dollywood is a wonderful place to visit
if you guys are going to drive through the mountains, there is a restraunt at the very edge of gatlinburg on the right (its the last one beside the gas station i think it might be called applewood) you can stop in there and get a picnic lunch that is very cheap. its neat because they have several adult ones and several kid choices and it was a lot of food. there is plenty of places to stop off and have a picnic. the highest point in the smokies is neat, but it pretty much is a straight climb up and the air is a lot thinner so if anyone has trouble walking or breathing i wouldn't recommend it.
one thing that i think is neat is the biltimore estates which is a little bit of drive but its very pretty. right now is a great time to go.
oh and my favorite is horse back riding. there are several down there and its absolutely breath taking. most of them take you up the mountains and around and back down. usually you ride for 30 minutes for like $15/$20. if you don't want to go up a mountain then its cheaper.
hope i helped some!!!