I'm trying to put together a bonsai course for mentally and physically
disabled people.

I would not try to put mentally and physically disabled people in the same
class. Also, what do you mean by mentally disabled? You wouldn't put people
with cognitive or emotional disorders in a class with the retarded.
The class would not be essentially different from a regular class, except it
would need to be small, with more individual attention. For further
information, contact the American Horticultural Therapy Association. They have
a Web site.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)