For my money, the ONLY way to go to Wisconsin Dells is to rent one of the Glacier Canyon timeshares off ebay. Glacier Canyon stays gets you waterpark passes for Wilderness Lodge...where there are three large indoor waterparks...something for everyone really. I've stayed twice in 2010, both in 4BR presidential units, which are absolutely massive (2600 square feet, and just beautifully decorated). Quite simply, nothing nicer in the Dells. And, here's the best part. One trip, my share was $125 for a M-F (not per night, TOTAL), and the second time, it was a quick trip for my children's birthday party...three families, two nights, and I paid $300 total (and I paid for the whole thing). That total got me my room, and access to up to 10 people to all the waterparks for the entirety of the stay.
There is no better deal anywhere at the Dells. Period.
To get these great rates, you have to be willing to go during the week...weekends will cost you more. However, what you get in return is very quiet waterparks, and a truly relaxing and inexpensive vacation.