I say offer everyone the opportunity to donate on the day. Don't turn it into an entry fee thing, for charity or not, it'll put people off coming.
I know what you mean, but wouldn't it be nice to have an annual charity raising event, with a chance to in some cash.
We could have a poll?
I'm cynical and I'd say no. I don't do charity. Flame me if you want but I choose to spend my hard earned and not give it away. I'm sure there are plenty of worthy causes but not for me. I'm lucky enough to have never been afflicted by anything that would prompt me to support a charity. Maybe that will change but at the moment, I don't feel the need to.