Re: Michigan or Wisconsin Family Vacation
Many great suggestions here already. Additional thoughts are Bayfield WI, camping in the UP, the Keewenaw peninsula, and the Porcupine mountains. If you like biking, there's the Ice Age trail in WI, and some bike trail near Sparta that's buried in geocaches if your boys like doing that. Willow River State Park in WI has nice trails and a waterfall as well as camping. There's some neat state parks near Milwaukee too. Check out the submarine in Manitowoc. The La Crosse area has interesting terrain with the bluffs.
If they are states you're going to visit regularly, try buying a book on daytrips for that state (or check one out from your local library, if you live close enough they have that state). You can use them to pick activities near where you'll be staying, or use your favorite activities to pick what part of the state you're headed to.