Sounds like D'Arcy will be a wonderful resource for helping you, but I thought I would chime in too since I have organized silent auctions for other non-profit events and reunions, etc.....
don't forget to list along with your starting bid an incriment in which all following bids must meet. You could alter this so that on items of lesser value the incriment could be $1 (Ex : if previous bid is $25 next bid must be $26 or more)
For your large value items, bids must increase at a faster rate, maybe $5 or $10 increments. So you could entice people with a lower starting bid, but the idea is that people will get close to the value in a matter just a few bids.
Just clearly print or announce this from the start so you have no complaints or confusion from the bidders.
P.S. it is my experience that there are usually items that don't reach their value. I have also seen items go to the first and only bidder who simply matched the starting bid. But if the items were donated, then any payment is profit for the cause.
GOOD LUCK - YOU HAVE SOME AWESOME THINGS LISTED FOR AUCTION!
Dawn (34) Pottsgrove, PA W-A-T Coordinator
Mya (4) delivered @30 wks/ emerg c-sec/ 3 lbs/ severe PreE/ remained severe after delivery