We visited several schools ourselves. Obersee was one of them. The problem for us with Obersee is that they were quite expensive, considering that they take alot of holidays. I suppose most schools are not cheap for this sort of education. The one in Wollerau is called Gemeni I think. The Obersee was very well organized, and already building a 2nd building to keep up with the demand.
We tried looking into the french school, but with out being a french by birth citizen, as it prepares kids for the BAC, it was too much as well. My kids, also 4, speak 3 languages, french and english the best. I do not know how long we plan on staying in Switzerland, but getting them more involved in the experience of being here, AND from what I saw at Obersee, Gemeni and others spending that sort of money for the kids to do what mostly turns out to is a play group, seemed a little crazy. They were in school last fall in France learning to write, do numbers, and even read. Everything I saw for their age in Switzerland, as every school is just basically playing. If they were older it might be a different story.
So we enrolled them into local Kinderhort, and now they speak more German then either of us. The "teachers" there speak in English, French, Spanish, and German with my kids. It seems to be working out quite well. AND I am not getting charged extra for things like after school, meals, and little trips. If they were enrolled at Obersee, I not only would be paying their tuition, but also paying the Kinderhort on all the vacation days the Obersee has off. We both work, so it's not practical.