At Jeff Bannow's suggestion I contacted Petosky State Park about their group campground. I was told the group campground is for use by youth groups, church groups, etc. I told them that many of us act as childish as possible, and we were all members of a religion of sorts, but I failed to convince anyone.
But Petosky State Park is still the Official Campground of Photostock 2011!
It was worth a try - thanks Dan! Eva & I will be camping there, as will Dan & Silke. It's going to be a happenin' place.