In Geneva for 2 months. School for 5-yr old?

Hi,
I'm likely coming to Geneva to work as a volunteer on a short project at the WHO (mid May to mid July Protected content , and have a nearly-6 yr old and a 2 year-old. Can I register them in school (public or private) for such a short time? Or are there French language classes? Welcome language classes? Or summer camps I could look at? The 5 yr old is in French Immersion in Canada (spoke only English until this year, but is now in kindergarten in French). I would like her to be learning French every day so she doesn't fall behind. The 2 yr old speaks only English. Any advice very gratefully received! Heather