Ok, where to start?
I am assuming if you are coming from NYC your dh is likely to be working for the UN? If that is the case then you need to be on a certain side of town for the UN as the majority of buildings are in one place called Gigiri (also where the US embassy is situated).
In the area around Gigiri there are many residential housing estates for expats and upper middle class Kenyans. In this area you are likely to find a house with about 1/4 acre of garden, probably 4 beds upstairs behind a security gate and 1 bed downstairs. Most of these houses also have a family room upstairs. These houses for the most part are 'modern', spacious and light, but slightly lacking in character. Power and water is also good in these areas. Rental prices in these areas are about $2000 per month. To buy you are looking at between 40,000,000 to 70,000,000 Ksh. Gigiri and Runda are the two closest estates, with the more upmarket Muthaiga also being quite close. Muthaiga is where the upper echelons of the diplomatic corps live. Lovely old colonial houses and bungalows often on more than a 1/4 acre but with bigger price tags.
We live slightly further away in an area called Kitisuru/Lower Kabete/Spring Valley where you tend to find more long timers, but there are still a lot of UN people around here. Rents are slightly cheaper, houses often older.
In both these areas there are a number of schools, an international school called ISK, which has a great setting and a good reputation, following an American curriculum. Numerous kindergartens (up to age 6), a German School, and a very British Prep school called Peponi House. My dc go to a local kindergarten and one goes to Peponi House, which follows a British curriculum.
If your dh needs to be working in Upper Hill or closer to the Central Business District, then you can think about the following areas: Lavington, Hurlingham, Kileleshwa and Riverside. These are some of the first suburbs and so there are some old houses if you can find them, but quite densely built up. Riverside is home to many lovely apartments but fewer houses. A lot of NGO folk live here and the lower echelons of the diplomatic corps too. There is good international school near here called Braeburn, though I'm certain which curriculum they are following. Also close to here is an excellent prep school called Kenton College, which follows a British curriculum. The French school is also in this area though, be warned, it has an appaling reputation even amongst my French friends!
Finally, the third area is slightly further out of town in an area called Karen and Langata. This is the area where Karen Blixen had her coffee farm and nestles under the Ngong Hills. Here there are old and new houses, normally on larger than 1/4 acre and slightly cheaper than either of the other two areas I have described. You will find here a great deal of the white Kenyan set, owning and running safari companies, running horse stables and the like. It is also drier on this side of table and there are water issues. Out here there are two big schools The Banda and Hillcrest, both British prep schools. Some folk send their dc into town to Kenton, some to Braeburn, both of which do a bus service.
Be warned, the traffic is absolutely awful, even for a New Yorker. Getting stuck for hours can happen on a daily basis, so choosing where you live and where school is is important from a location perspective as much as from the type of school you want. Also there is very definitely a different kind of people living in each of the different areas so you need to consider the sort of social mix you want for yourselves and for the dc.
I will go and get some links ready too....