We absolutely love Gatlinburg. We go every April and usually at Thanksgiving as well. Our DD is 6 now and our last trip was her favorite by far:
1. We stay at the Wilderness Waterpark. It can be pricey so we are going to the Wyndham next to the Wilderness this April. If you stay there tickets are very reasonable to the waterpark. Con: long drive to the Park.
2. Wild Bear Falls is an Indoor Waterpark that you can buy daily tickets for.
http://www.wildbearfalls.com/ Not as nice as Wilderness but definitely fun for a day. You can enter and exit if you want to stop for lunch or dinner or other activities.
3. We love Cade's Cove. We tour the Cove each time. It is 11 miles and usually including the drive to and from we spend about 4 hours on the tour. 1 to drive to and from and 3 at the Cove. Last year we saw two cubs within a few feet of us and two bear families on the drive back.
4. The Roaring Fork Trail is amazing. However, not for the faint of heart drivers. I drive a very wide crossover and we did some scratching and really scraped a rim. That trip was as it was getting dark. We saw a lot of wildlife on this trail and it is not packed with tourists.
5. We love the Rock shop as you enter into Sevierville. The staff are super friendly and even rearranged their entire shop after DH (who is paraplegic) struggled on our first visit. To our surprise on our second trip the shop was rearranged and the staff member came out and explained why. We like to mine for gems there and buy small pieces. I usually buy a couple of the small bags of dirt for surprise gifts during the year and DH and DD mine at home.
6. We enjoyed the NASCAR Speedpark in Pigeon Forge.
http://www.nascarspeedpark.com/tn.aspx They had a special going the last time we were there and we got wristbands for less than $10 for the entire day.
7. We eat at The Apple Barn for the apple fritters.
8. We always do the Ski Lift and recommend Uber Gatlinburg at least once.
So sorry for the long post. We really enjoy this area as you can tell. If we want to spend most of our time at the park (and April is a good time for wildlife) we stay in Gatlinburg at a cabin. We rent through American Patriot Getaways and they have fair prices and respond well to any issues.
http://patriotgetaways.com/
I hope you have a great trip!