I think you are right to have things pre-cut. Yes, it would be great to teach basics, but it would require more than one day. This will give them a taste of quilting, and what they really want is good food and a finished product to take home. How about a quillow, with big blocks, and making a sandwich to finish? I also like the idea of a rag quilt. Find a local guild that would be willing to donate batting scraps. They may also be willing to help pre cut or even come and help for the day. Just some thoughts.