We are in Ontario and all the radio stations advertise "Come to Michigan" all summer long, but they probably don't advertise right at home. I signed up at Michigan.org several years ago and I get weekly email ads for all kinds of events all year long. Signing up for Michigan DNR also gets you on an email"hit list" with events at State parks.Don't know if that happened when I booked a campsite or if I had to sign up separately.
Good luck on camping with the family, our kids still enjoy camping, and we took the "baby" (25 years old) with us for Canadian Thanksgiving weekend.