On your way over to Gaitlinburg, make sure you stop in Asheville, NC. The Biltmore estate is there, which is a fantastic stop. You can then drive through Smokey Mountain National Park to reach Gaitlinburg. Leave yourself enough time to pull over on the side of the road a couple of times and explore the scenery
Thanks - we ended up stopping at the U.S. Space & Rocket Center in Huntsville, It was a quick side trip off the main route and we all really enjoyed it. My youngest is even doing a report on the US Space program he enjoyed it so much.
We were able to visit St Augestine and take the trolley tour and had a great time. I love archtiecture so it was a special treat for me. I will be recommending St Augestines to others for now on!
Have you ever checked out Chattanooga? It's a great small city with some beautiful architecture, interestig cultural stuff happening, and history museums, zoos, festivals, etc. There's some basic stuff here: https://www.tripadvisor.com/Attractions-g54946-Activities-Chattanooga_Tennessee.html
Also there's some really great food!
Atlanta, Georgia is a lot of fun. And very close to where they film The Walking Dead if you're interested in that. There is a cute little town near the film set. Also, Athens is a great town.
I would really recommend Savanah, Ga. It is probably the most beautiful city in the US in my opinion and certainly has it's share of history!