here's a few to get you started...but you can just google "free quilt patterns" and you have tons to choose from
http://www.scrapquilts.com/0101bom.html
www.missouriquiltco.com
www.quilterscache.com
also you can put "easy patterns" in the search box above plus most of the fabric manufacturers (Moda, Benartex RJ Kaufman etc etc have free patterns on their sites. Good luck and happy you are doing charity quilts!