If you pay some staff/crew and utilize volunteers for other positions, I'd suggest a few bonuses for each based on their job performance, attendance, recommending other good staffers, etc. Volunteers are not paid but it would be nice to give them an end of season gift of some sort. It could be haunt merchandise or maybe and American Express $25 or $50 gift card. Something to show that you appreciate their efforts. If utilizing a number of volunteers from a non-profit organization, I would strongly recommend making a donation to their group based on the number/hours of volunteers they provide. As for the paid staff, offer incentives as mentioned above.
"Follow the Bloody Brick Road"
"Keep 'em Screaming!"
"Whatever, whatever", "Whatnot", "Dah, dah, dah, dah"