I live less about 45 minutes away in the Lake Wisconsin area. We have 60 miles of trail and we groom them to perfection. I'm the President of the Yellow Thunder, the local club. When we have snow, our trails are hard to beat. Stay away from the Dells though (the City), because the trail goes down the road and sidewalk to get across the bridge. It is a mess. Same with Prairie du Sac. Otherwise, sledding toward Devil's Lake, Reedsburg and around back toward Lake Wisconsin is very nice.
A lot of the water parks are actually in Lake Delton, which is less of a mess compared to downtown. I do not know that you can ride from Great Wolf or Kalahari. But, it wouldn't be far to get to the trail.
I was at the Tommy Bartlett water ski/stage show a few weeks back and it was pretty decent. Not as great as previous years, but still good. Losing all the water in the lake last year resulted in some of the ski talent going elsewhere. Entertaining though even for your 3 and 6 year old. You might want to consider that as well.