I am not practicing, but I'm technically a lawyer ... so I would worry a bit! My recommendation is that you contact the IL bar since they prob'ly have lawyers that will help you pro bono. My general understanding is that with a not-for-profit you wouldn't be personally liable for damages but that doesn't mean being sued (even if you win, etc.) is pleasant ... I hate to discourage you from doing something so wonderful, but I do think that it's best to check into these things and get informed ahead of time. Good luck. link below ...
http://www.illinoisbar.org/
http://www.illinoisbar.org/