A lot would depend on what you consider fun, interesting and relaxing, Marysue. Are you looking for something outdoorsy? Or museums? Shopping? What comes to my mind would be either Milwaukee or Chicago. But, again, it depends on what you enjoy.

What kind of day of are you looking for? If you want a city trip, I would suggest driving down to Chicago, parking at a park and ride ($2.00) buying a day pass for the el ($5.00) and taking the Blue Line into the loop, and doing some shopping/walking/exploring in the city.

Perhaps Devil's Lake or another park? Maybe pack a lunch and go hiking/swimming/sunbathing.

You might consider heading to Milwaukee and if you don't choose to power-shop or go the the Art Museum, you may just want to head to the lake front just north of the Art Center. There is a nice little coffee shop called Alterra's along this stretch and it is a nice place to sit outside with lunch or coffee. After that I would head to the Old Third Ward and just enjoy the area. There are some interesting shops that are good for browsing.
http://www.historicthirdward.org/

I would get up early and drive to Mineral Point. There is a wonderful little cafe at Shake Rag Alley to enjoy a later breakfast and coffee. You can also walk around the buildings and see the artwork. Then I would tour Pendarvis. The tour is about an hour and the gift shop is nice.

Then I would hit the shops on downtown. Just enjoy looking at the galleries and fun little shops. http://www.mineralpoint.com/

I can't remember the name of the small restaurant but it was a micro brewery on the end of Commerce Street. They even have home brewed root beer and cream soda. Friendly place for you to have lunch or dinner on your own.

Take a drive down to Galena, IL. It is a very pretty little town.