We've visited 6 out of the last 10 Columbus Day weekends because it's our Fall Break here in ATL. Our break is Thursday (before Columbus Day) through Columbus Day Monday, but there are local variations around that weekend, and often you see guests that may decide to pull kids a day early or stay a day later.
There is a lot to do, which is fun, but also attracts people, for example, MNSSHP and F&W.
Weather has been good for 4 out of our 6 visits. And by good, I mean, hot - 80s and 90s (note: I like hot weather). For 2 out of 6 visits, weather was not good, including Hurricane Matthew in 2016 (which disrupted a lot of travel) and the Saturday and Sunday in 2011. I think the weather attracts a lot of people who want to use the pool, but don't want to deal with the extreme summer weather (hot, humid and thunderstormy), or the September peak hurricane season.
It's busy. Expect to see 150+ minutes for 7DMT.