As a BSA adult advisor I did both Mirror Lake and Devils Lake for many years. If you really want to get your “huff” in go to Devils Lake. Just do the high trail hike all the way around the lake. Looking down at eagles soaring over the lake is worth the entrance fee. There are also other “Glacier Age Trails” most folks never do at Devils Lake. Devils Lake campgrounds are the most used in Wisconsin. Quartzite campground has the first 25 campsites as first come first served. You need to get there mid-week and pick campsite #1.
Mirror Lake is surprisingly quiet considering how close it is to the interstate. Beautiful place to camp.
Other than the strip in the Dells. There is the rail road museum in Friendship. The circus museum in Baraboo. For a real treat go here for breakfast or lunch.
http://broadwaydinereats.com/
Hope this helps.