one response...from someone who won't be there...at this point, I'd think twice about putting a lot of effort into the project .

If you start to get a lot of positive responses (and I hope you do! ), those are the people who should say yay or nay to the T-shirt idea. Maybe figure out how many you'd have to order and how much they'd sell for, and take pre-orders. If you get enough pre-orders, do it...not enough pre-orders, don't. That would also help you know what sizes to order.