I did same kind of workshop with the preschool children before (scroll down if interested). I think it is a very important subject and kids adore it. After all these are great stories, filled with power, imagination, super powers and mystery.
This time around I offered them quite dark materials but no one complained. Instead they created, enjoyed and did a family of Pegasus (guess who!)!
See monster Medusa
One eyed giant, Cyclops
Monster of riddles, the Sphinx
100 eyed Argus
Monster of 9 heads, one is immortal, Hydra