Check the National Parks website for info on hiking trails and their difficulty rating because I'm not sure about them. The 2 I can say to visit is Clingmans Dome and the hike to it's observation tower. Easy 1/2 mile hike to it...all up hill. Hopefully you will have a clear day to do it because you can be in the clouds in an instant up there. It's the 2nd highest point east of the Mississippi. Stunning views.
Trails to many waterfalls are usually jam packed with people I can tell you that much. Parking can be almost impossible at some of them. The other place is Cades Cove at the west end of the park but it's drive through with places to stop and see some building and read about the history of the small settlement. It's an 11 mile loop drive that can take 4 hours to do, really, not kidding. The park is the most visited in the NP system so crowds are common depending on time of year. It's also one of few that do not charge to get into.
If you do go up to Newfound Gap and Clingmans Dome consider going into North Carolina to Cherokee. There is a working mill you can stop at before you leave the park and there is the Oconaluftee visitor center. You might see the Elk heard around there if lucky. Cherokee has the Museum of the Cherokee Indian and it's worth a see. The town itself is full of Indian trading post gift shops and of course there is the Harrah's casino there too.
Dollywood is a nice park and family friendly to the Nth degree and if you get there early like when they open a day should be enough to cover it all. If the kids like coasters then have them ride the Eagle. Rides for the kids and shows for the "old folks". Tickets run about 70 bucks but considering Disney is 120 now that's a bargain I guess.