Hi Judy,
Yes, I've had this happen when I've taught the Dia del los Muertos unit in
Art. Because it is such a touchy issue in the school setting (of my
district, anyway) I was required to have a signed parental form from the
parents of every student in the class. I re-packaged the idea of the
lesson, which was really to do figurative paper mache sculpture. In the
letter home, I offered to let parents review the curriculum unit and I
offered an alternative assignment, which still met my curriculum goals. The
students whose parents have objected have been fundamentalist Christian and
Pan-Asian.
How about if you re-package the mandala as "My interests and hobbies"? That
imagery will still meet the goal of creating a symmetrical circular form of
art.