I suggest you decide right now that you will only accept donations of 100% cotton fabric. You will be amazed the kinds of fabric you will get if you don't put limits on it.
Do you have experienced quilters or all levels of experienced quilters? If you have a mixed group, pick a easy pattern that everyone can get done in a reasonable amount of time. Maybe a 4-patch or 9-patch... that way you could tie the quilts instead of quilting them. They will get done much quicker.