Have you tries sidewalk drawing? Maybe try a copy of the masters,Van
Gogh and his Sunflowers. Another cheap project are the starch packing
spagetti that come in boxes used to ship medicine. Try your local
veternarian or hosp or doctor or any thing that gets fragile objects shipped.
The kids stick them together when they lick them and they make fun sculpture.
I tied this in with disposable art (Christo) and asked if art was
meaningful if it only lasted a few hours, days or did it have to last for
centuries. The sculpture disolves with water and we had fun washing it
down the drain. Hope this gets to you.