Hi - what a range of choice you have!

Cologne is a lovely area, but yeah you and the kids would wind up having to learn German. And there are the schools - not only do they start kind of late in Germany, but the kids only really go a half day, which makes it difficult if you're interested in working.

Westchester in NY would seem to offer the widest range of choices. I don't have the details, but I'm pretty certain there are French language schools available in the area. (Private schools, of course, but it would certainly keep the kids up to date with their French.)

Westchester county includes some very well-to-do areas, though the public school systems vary by district (as is always the case in the US). You can start here in researching the area: Westchestergov.com The Wikipedia also has an interesting article on Westchester Country. And if you Google "Westchester County" you will find there is LOTS of information online. Of course as a suburb of NYC, you have access to all the cultural and other resources of the city.

It would be a very different lifestyle than Switzerland, but certainly one to consider.
Cheers,
Bev