Kid-friendly Wisconsin winter vacation spots?

You are a brave man heading to Wisconsin in late December!

I'm actually British but my wife is from Milwaukee and i've spent a bit of time in badgerland.  I ran this question by her and here is a suggestion.

Venue: - Country Springs Hotel (off the highway in Waukesha).  It's got a pretty cool waterpark, loads of affordable rooms and is very well located for getting to Milwaukee (some good museums for kids); shopping; ice skating at the Pettit National Ice Center; also have the Bucks (NBA) and Admirals (minor league hockey).  There are also a couple of nice museums and things to do in Madison, such as wandering State Street, which is also not far from Waukesha.  There is a famous museum type place called The House on the Rock which the locals all know but i have never been there myself.

You could always head up to Wisconsin Dells (lots of indoor water parks) but I'm not sure what it's like in winter.

Maybe check out travelwisconsin.com?