We spent one night at home before heading out for a camping experience at Silver Lake State Park. It was just one night but they got to experience something all kids should experience -- sleeping in a tent under the noise of the wind in the trees and eating s'mores around a campfire. It worked out well. Most everything went according to plan except the weather didn't hold up and they couldn't take a dip in Lake Michigan. But we got in some canoeing on the White River and they did get to swim in Silver Lake which is a lot warmer than Lake Michigan anyway.
The next day we took the Sandy Korners jeep ride on the sand dunes. These are the only sand dunes you can drive on unless you want to head out to Utah. We were out there last year but I didn't really consider the jeep ride due to the expense. But it was well worth the $90. Really an excellent experience and highly recommended.