Try contacting TSV Solln (a sports Verein in the south of Munich - not as far south as
Starnberg though I'm afraid). I used to take one of the kids I looked after to a gym group organised by that club but if you are after serious gym coaching then maybe that is not the place for your kids as this group was more about letting the kids climb over everything, jump up and down on the trampoline, have fun in a slightly structured format- ie. not a place for breeding future Nadia Comaneci's.
TSV Solln Turnen