If you want to do it on your own, you could rent a pontoon boat for 1/2 a day and enjoy the river on your own. Bring a grille and enjoy. The lower dells are much more scenic than the upper.
Have fun. Yes it is very touristy, but if you know exactly what you are going to do and you don't stop at every single place it is very pleasant. We stay at stand rock campground just outside the Dells. Very nice place. The property back to the Wisconsin River and they have some nice trails that go back to the edge of the river and you can wade on the sand bar.