Auctions are a lot of work
but can be very rewarding for the school.
First off, unless C market has changed they don't take any money up front but they do take a large chunk on the back end. read the fine print. the more you make the lower the persentage thay take BUT it use to be 9% of the first 50 or 75,000. THEN there is the problem of having to keep double track of the information. They don't handle any of the registartion for your event and they don't handle any of the tac infomation. you hav to do it in a separate software.
If you are going to run an auction, I say go for all of it. you will find that some donations will work online, tickets, skating time, pods etc. some items work well silent, plants, quilts, painting (things you don't want to have to mail out after the auction) and some things will work well live, pricipal for the day, teacher fun thins trips etc. If you are going to have to solicit anyway....
I do think the *trick* to all of it is finding the software that fits your budget, there are a few good ones, I pesonally like MaestroSoft/MaestroWeb, they work together to have all auctions and EVERYTHING is entered once. You can keep track of mecendice sales and raffle sales too as well as all of the registration stuff, sales and well everything.
You have time to look into the auction software available out there and plenty of time to figure out what you really want to do in terms of your event.