Thanks everybody for the warm welcome and your helpful hints. The "capsize corner" is a great ressource with lots of valuable insights! I also like the idea of carrying a VHF or mobile with me, in any case the device itself should be waterproof.
David, I will be at lake Garda the week before Easter, it's the world's biggest Optimist regatta, and with 1200 competing boats very likely the biggest sailing event at all. I suggest to change the Optimist class rules, bringing an Aero should be mandatory for all parents, so much more fun than batteling with the other parent's who's first at the slip ;-)
Best, Thomas