Maybe I'm way off on this, but I think that this would be a great opportunity to make a Geuze! It will require much patience (years!), but I think that this quantity of old hops is a great reason to do it, especially in a group setting where many people can share the bounty of many gallons of geuze. I would love to do it, but I can't imagine ending up with 15G of geuze a few years from now...I don't drink it that fast.
I've read that you need "aged hops" for a geuze. Some people put hops up in the hot attic for a few months to accelerate the aging process...the goal is to get less bitterness and aroma from the hops and instead to just use them as a natural beer preservative.
Anyhow, find a good geuze recipe and make a batch with the proper yeast/bacteria when you guys get a chance. Rack and store it for a year, and on the 1 year anniversary of the first brewdate, make the same recipe again. Repeat for year two. On the third anniversary, make another batch. Repeat. Four years from now, you'll have some 3 year old, some 2 and some 1 year old lambic. Carefully draw off small samples of each and taste. Blend them such that the different characteristics of each vintage complement each other without overpowering. When you have the ratio that works, blend the different vintages and bottle to 4 volumes CO2.
Good luck, I'd love to hear what you guys end up doing!