I'd start by pulling out fabrics, and put them in colour groupings.
Then see what measurements you have and types of fabrics ... then what patterns they will work with.
If doing "scrappy", I'd suggest it be kept to somewhat organized. Some people don't get excited over a real scrappy look, as they see it as messy, leftovers and a jumble. Though some lovely scrappy quilts can be made where the colours just blend and meld and you go WOW!!
Sizing ... a queen is versatile as it still works nice on a double bed as a full spread and while not a spread for a king, works as a top cover, just not as a spread.
Consider if there'll be enough tickets sold to warrant the larger size ... if it's not a large sale opportunity, then perhaps a Lazy Lap quilt would be just as appropriate. You don't want to give away a huge quilt, if the group is not making enough returns.