My friends and I have gone camping at Jellystone in Warrens almost every summer since we were in high school - they've expanded so much, and camping is no longer required, cabins and a hotel like building are all available. It's a great destination, but you have to drive a distance to get to anything other than Jellystone.
Spring Green Wisconsin is also a really neat scenic place; House on the Rock is an amazing place to go and explore.
Galena, IL is also wonderful - my cousin got married there last summer, and the town is just beautiful - built into the side of a hill, it's an old town mainstreet with neat shops and stores and whatnot. There is a large golf course/resort just outside of town, otherwise Dubuque, IA is only about a 15-20 minute drive away, with lots of hotels (the Hampton Inn there is only a year or two old, and has lots of great amenities - I used to manage one, and the one in Dubuque is great!) Galena/Dubuque are a bit more of a drive than some of the WI destinations, but would probably be my main recommendation.