The Guild I attend keeps the stash in one designated place and is available to all the members, when we want to make comfort quilts, we just "shop" from the Guild stash, no charge. But it is designated for comfort quilts only. Last month the ladies in charge of the comfort quilt ministry put together kits for pillow cases. One of our local charities, The Marjoree Mason Center, had requested pillow cases. We took the kits home, sewed them up, and then returned them this month. This way even people who can't afford to buy extra fabric can make comfort quilts; we do other things for fund raising.
Having said all that, I think the way your guild is doing it is good too. After all, we all love to buy fabric, so why not buy it from your local Guild? Good luck with your sale!!