Uhm, the auction sounds fine, but you would need to auction targeted stuff!
There's a stuff they do here in Italy every during city fairs, not sure if they do it also anywhere else: we call it "la pesca", literally "fishing". You put many things together and then you do a sort of lottery: whoever buys a ticket, would get a random number, which would correspond to a prize. Complaining won't be accepted!
Other idea: organize a big bingo night. Organize 5 rounds with a maximum number of people (e.g.: 50 each match)
Prices for: two numbers on the same line, three on the same line, four and five on the same line and then bingo.
Entry ticket for each card to play.
If I get to think of anything else, I'll reply. Good luck!
Glad you liked it! Let me know if they choose it and if you raise enough