A.C.
We live in Madison, WI, and went to The Dells for a day a couple years ago. Went to the upside down house (not worth it for the price), went on a Duck ride (really worth it; we enjoyed the ride, and they give a lot of fascinating information), and went to the deer farm (definitely worth it. You get to go inside the farm and feed the deer, get close to them; some of them will let you pet them. They also have elk and ducks and goats--everyone in my family enjoyed it. It might be open in the winter.).
But I also agree with all the other posters that you'll probably find that you'll have more than enough to do at The Wilderness. That's something we've been talking about doing before my daughter gets much older (she's 11), going to and staying at one of the indoor waterparks. She also wants a weekend at The Mall of America. So we'll have to see which one we can get in for a vacation. ;)
Have fun!