Moving to Nairobi! Cost of living for family?

Hi all,

We are a german family moving to Nairobi in a couple of months.
Could you please tell me the approximately cost of living for a family with two babies (2 years and new born)? As I checked in many Forums, we prefer to stay in Gigiri area, in a closed Compound, where we can have contact with other families and to be near the german school / kindergarden.

And how about the food, car, made, gardner, electricity, water, telephone etc...?
Should we have our own car and drive by our selves, or can we hire a driver?
since we drive in Germany on the right side...

How about safety? Can I just go out with my two babies for shopping?

I will appreciate your answers and thank you in advance