styro foam cup printing - might make a good relief/substitute teaching piece as well (fairly unique) - but instead of paint, maybe use a cup and ink pad, colour in with markers or crayons, or pencils (whatever is on hand and best to use with that particular group)
3-D coffee cups. These are espresso coffee cups printed out of Glazed Ceramics. The printing process takes almost a full day, and the One Cup a Day project aims to design and create 30 unique cups in 30 days. You can purchase their creations from this website where prices range from $36 to $77.