Oh, man! That sounds like a ton of fun, but I'm already booked that day. (Yes, thanks to kids and vacation schedules and family reunions, the summer is filling up already.) We leave on the morning of the 6th for a driving vacation with S's family - the 5th is going to be spent packing the van with a week's worth of supplies.
Can I interest you in the Ann Arbor Art Fair, two weeks earlier? It's really four separate art shows, which means its lot bigger and outdoors, and probably has all those folks plus more. http://www.annarbor.org/artfair2005/
I generally hang out around Main Street (because I work at a bookstore there) but also take the shuttle around to other sections. Yes, there is a lot of walking involved, and parking is an adventure. Tons of fun!