Hi
You've chosen perhaps the best time to come and live in Geneva, summer is wonderful. We live in Geneva, but on the right bank, so not of relevance to you.
I don't know the left bank very well in terms of housing/schooling options, but the area around Parc Betrand on the left bank is lovely, very metropolitan with streets of mansion blocks turned into apartments, overlooking a lovely big leafy park which is excellent for children. Geneva is known as the 'city of parks' and Parc Betrand is one of the reasons why. But it is built-up because it is very much 'in town', like the Upper East Side NY with central park on your doorstep. That might be more what you're used to from NY or Paris when you say metropolitan.
Mme Lindor mentioned the Chene Bourg or Chene Bourgeries areas, which from flying visits, I get the impression are nice although don't know them well. (There is a brilliant children's festival in the park next to the town hall in Chene Bourgeries called BimBadaBoum, every year in August - highly recommended. It is the epitomy of how brilliant Geneva is for children/families in the summer.)
If you type "montessori geneve" into Google, that will come up with a list of montessori schools and you can Google Map where they are. This one says it is a pre-school for upto 6 years old (bilingual) and located near Chene Bourg just on the Swiss side of the border. www.littlefriendsmontessori.ch/Pages/English/
I find the public transport here is superb, so even if you are living a little outside the main city centre, getting to work in Geneva centre shouldn't be too much of a problem. (Although they have just revamped all the tram routes and people are a bit up in arms about the new timetables/routes!). You can check public transport routes here
www.tpg.ch/fr
Hope this helps, will post again if anything else comes to mind.