There are so many clever ways to make fabric and felt flowers. How about taking that a step further and make pins or magnets. Step it up a pace and make headbands. Good idea about the yo-yo's. Use them to make pins and magnets. Since you are the quilter, how about helping them make a simple quilt block which can then be turned into a pot holder. I do like the idea of hexi's and applique because that is something they can continue, long after you've returned home. Remember that the most important thing is for you to have fun and instill in them your love of creating.