I was at Vista Way 2005 so I don't know if I can be much help, since I never saw Chatham(sp?). I would take enough to make your stay nice, but as little as you really need. You can take the bus to Wally World if you need to to get essentials. Remember, you'll have to pack it all up to take it home. I think I only took one suitcase full of clothes and I was fine. I was in costume working most of the time. So think less is more! And only take things that you won't care about leaving once you do leave. I had the problem of accumulating too much and almost didn't get anything back home lol.
It's like staying in a dorm room really, not much space. And I would suggest a shower caddy that you can haul from the shower to your bed. I only got a bed, a dresser, and a nightstand. But really, you're hardly in your room at all. Hope this helps some, it has been so long since I went!