Paper making. Bring in old newspapers, blenders, and some spare screens (like from windows, the finer the mesh the better). And food coloring. Blend paper and water into thick pulp. Add food coloring if desired. Spread on screens to dry. At that point you can add in other chunks of construction paper in neat patterns, and people can have their very own homemade paper for whatever they want to do with it.
Simple bookbinding is also pretty easy to learn how to do, and everyone gets their own little notebook.
Depending on the interest, mask making. Get paper masks, and bring in markers, crayons, glue, glitter, feathers. Go crazy with it. Then have a "fashion show" afterwards and take votes on several categories. Best use of color, best design, craziest, most fitting to the individual's personality.
Sugar cookie decorating. Crafts plus desserts. Everyone wins.
Paper mache crafts - you can make mini pinatas with them, or just do it over balloons to make neat new bowls for at people's desks. They won't hold up forever, but they're fun while they last.
Pipe cleaner art.
Wooden sticks/tongue depressor crafts. Bookmarks, buildings.
Make teams. Challenge them, who can use this set group of craft supplies to build the tallest structurally sound tower? It has to balance an egg on top for at least ten seconds without falling or collapsing. (Hardboiled egg, of course, to make it easier to clean up.)
Decorate plastic eggs. With paint.
Also, by the way, I'm totally jealous of your job. I'd love to be in charge of crafts and activities.