The caverns themselves were kind of neat, but wished we could've done the tour without the guide. Lots of thinly veiled (or not so thinly) conservative comments (such as "They don't make men like they used to") sprinkled throughout the whole thing followed by "You're in Tennessee, we tell you what we think." I think we only learned one or two facts from the tour that we found genuinely interesting.
Great stop! Won't suck up too much of your time, kids are going to love it! It's incredible inside, totally magical. We really wanted to stay the night there, but all their rooms were booked up (make a reservation early!) The restaurant had a 45 minute wait, so get your name on the list for that before you walk around exploring.