we went in february, its beautiful.
I recommend driving thru the park, going to cade's cove at least once while you are there. Its free.
In townsend there is a place you can go tubing in the river which looked like it would be fun, although in winter we couldn't experience that.
There is a winery in gatlinburg, and also an aquarium which comes highly recommended.
Many shops & places to eat... Take the kids to the big Christmas store for fun- they might like that (you could get a personalized family ornament done) and the other Christmas stores are just as nice for ornaments, too.
THere are plenty of pancake joints on the main strips. Kroger is the main grocer chain there.
The great american steak & buffet company was good eats for cheap...family friendly, they have a band there and tv's hung all through the restuarant. Other nearby buffets : Shoney's (try the breakfast buffet), and Golden Coral.
For the more adventuresome in the crowd there is
Zorbing. Only a few locations worldwide that have this.
Plenty of places to go to for horseback riding as well.
In townsend,
Miss Lily's is a great spot for a quiet and peaceful yet yummie lunch.
Also in townsend (the quiet end of the smokies) is the
APPLE Valley Farms & Country store-- its pretty big, there is a small concession style "barn" where you can get fresh apple fritters/ apple foods, also a small indoor restaurant and a general store with a lot to see. (the website in that link will also link you to many interesting places to see/go in pigeon forge area.)
Lodging in townsend on the river, $75/nt summer rates.
Overall, its as expensive or cheap a trip you'd like to make it. Just make sure to take lots of memory for the camera & the batteries/charger. Have fun, its a beautiful experience!!