I vacationed there a few weeks ago and SMKW is not to be missed. Your family will even enjoy spending some time there and you will most likely not get bored for hours. It is pretty impressive.
A mile or two to the south toward Sevierville there are a couple of spots that offer helocopter scenic tours. I didn't want to spend a lot of money on that, but they have prices starting at $10 per person and it is a real blast for even a brief ride. Don't miss.
The muscle car museum is about 6 miles south of SMKW. I didn't see it myself. There is also a warbird museum at the airport in Sevierville. Just didn't have time to get to that, either, unfortunately.
In the Smoky Mountains park, stop at the visitor's center for advice. They also offer a shop, museum and movie. An easy but very enjoyable hike is to Laurel Falls. Doable with kids. It is smart to go to the park early in the morning and leave before lunch time or at least early afternoon. This way you will avoid traffic, crowds and heat. Bring bug spray and water. As stated above, the drive over into NC is very scenic.
There are a million things to do in Gatlinburg. Almost overwhelming. I didn't see the Ripley's aquarium, but is supposed to be very good and will fascinate the kids for sure. You can spend hours just walking around and finding interesting shops, etc. There is also a cable car ride or something up to a nearby mountain top. Kind of cool.
We enjoyed the area very much and will likely return.