I am chair of out guild's charity quilt committee. We use whatever is donated to us. Some of the ladies use fabrics from their own stash and the fabric choice is up to them. I make up kits for members to take and make up from the donated fabrics. The only donated fabrics no one wants to use are the polyester double knits so I take those to the thrift store.
Remember the quilting tradition is to "use what you have available".