Dale,
Believe it or not, what side of Ann Arbor you will be frequenting can make a big difference. Think of A2 as a sod plug from the East Coast Megopolis. You don't want to drive across it if you don't have to. It is surrounded by interstate and plan to use that to you advantage.
If you are going to be in and out of south side of Ann Arbor, the parks up on I-96 are actually quite far. Study your expected routes.
Wayne County is you typical fair ground camping.
The amenities at the Detroit Greenfield are much nicer.
I personally would never stay at either Detroit Greenfield or the Wayne County Fairground. They are walking distance for me. I did like in A2 for a while and am frequently back there for visits.
Matt - a refugee from the megopolis.