do 9 patches, 4 patches, and log cabins... let them all vote on their top 5 colors and chose 2 or 3 from these...a limited color palette can help it all go together for beginners... they can all handle that.. give them one block to do and then have a second choice for them if they like it enough to get done with that one... you can always fill the quilt with plain (solid or printed) alternate blocks... be sure to put a border on because it will look so much finished when hanging in an art show.