Um I don't know if this is really what you're looking for but our gym's part of a really big sports centre and every couple of months they have a free fun day, anyone can come in and see as many of the clubs as possible training (the swim team, the taekwando, our gymmies (we're the best ha ha

) and they usually have other stuff on too- bouncy castles and face painting etc.
We usually do a few routines and stretches for them and then do some stuff like bouncing on the tramp and walking along the beam and jumping off with the younger kids. Its fun, and we usually get quite a few new people in that way.