We spent 10 days in Wisconsin Dells this last summer and had a very memorable time. We split our accomadations between the KOA and Jellystone Park campgrounds. Jellystone Park has a wonderful pool area with many kid friendly activities but we did find the park was overcrowded and it did damper our time spent there. The KOA was a little more low key but still offered a decent pool area.
As far a as attractions there is really plenty for all ages. Our kids are 7,6 and 4 so we stayed away from Mount Olympus as we thought we'd save it for when the kids were older. Noah's ark was a highlight for all of us and we could have stayed in the wave pool all day. We also hit the Deer Park, Tommy Bartlet show and the Original Wisconsin Ducks. Would definitely recommend all shows. The shops downtown offer much to choose from and makes for some nice strolls.
We normally like to make sure never to hit the same place twice in our efforts to expand our areas but we know we will have to come back soon!