Hi, Joe!
    I don't see how this would be any different than buying a ticket to the non-profit theater I work for- those are not tax-deductible.
    It MIGHT be if it were a $20 SUGGESTED donation, but letting anyone in, even if they don't pay. If there's no way to get in without paying $20, don't call it a donation.
I'd always say err to the cautious side- I doubt it would bring in many more people anyway.
    (I'm not in any way qualified to give legal advice, this is just the hunch of a young lad who's Tech Director in a Non-Profit.)
    Best,
Kristoffer Ross