Favorite spots in Midwest?

Thanks for the suggestions so far, I'm thinking more trips are in our future! By summertime kids will range from 9 months to 12yo. Thier not picky about spots as long as the campground has a pool and a basketball hoop. We've done everything from the nature sights to the man-made sites (e.g., museums, science centers, etc.). As with any childhood experience we're out to make memories! Camping has been a great adventure for our family and momma is ready for a little longer trip!

Thanks again everyone.