If we are still in the "looking" phase Rich, how about Coldwater Lake in Isabella Co.? Here's a link to their webpage for Coldwater Lake Family CG: Coldwater Lake Family Park
I know nothing about this lake other than what I've gleaned off the web. It does have a few islands and a depth down to 60 or so feet. The campground does look like it has all the "prerequisites" also. Just more food for thought.