Hi Gail - this sounds like a tall order; multiple handicaps, wide age range!
Probably widely different intelligence levels too. Two things come to mind
that are pretty fool proof: stenciling and using templates to create various
kinds of repeated patterns: you can use chalk, colored pencil, tempra paint
(depending how messy you can get with a cariggt) . You can cut out some
stencils beforehand if you don't have any, they can be free form//absract, simple
geometric shapes, etc. If the students intelligence and motor skills are high
enough they can cut out their own stencils. You can also introduce
overlapping and color blending with basic stencilling. Stamping is a variation on
Basic guidelines are to keep it as simple as possible in the beginning until
you know your audience and
do as much prep initially to help the students get going - hope this helps!
- Pam Whisenhunt, Kingsbury Day School, Wash., D.C.