If it's possible, a well-located reserved parking spot for the year (or half-year) works very well for our school. There's a first-time investment of painting the spot and erecting a sign, but it can be sold (and markets itself when clearly marked as for the PTO Auction Winner Parking) year after year.

We just did this and a few that we used were: eat lunch with a teacher, principal for the day, teacher for the day, teacher helper pass.
Hope this helps.

Our PTO is looking for no-cost items to "sell" at silent auction at our spring fundraising Ice Cream Social. Items like read morning announcements or take a ride in a police car to school. Any ideas are appreciated!