Summer camp Switzerland

Hello,
I have been living in Switzerland for the last 10 years. I just saw your posting. My two boys went to Summer camp in July.
For French Language, a wonderful Summer School is Ecole Chantemerle in blonay. There were children from all over the world and local children learning French. They also offer English and German language classes in the Summer. Science camps too in English. Lots of excursions, games and activities every afternoon. Very nice camp but book early for next year they were full in July and had more space in August.
Regarding French, the academic school year offers the French Immersion program, which is like a study abroad program for locals. A child can learn French in one school year and then enter the public system or continue in a private school setting.
Good luck! It's great your children are learning French!