Good morning, and welcome to the forum, again.
District 4 is big. It has a few nightclubs, beer bars, but also very nice childrens play parks.
This is an example of a play group in District 4. http://www.spielgruppe-strolch.ch/
Werd is the city centre.
For me, it would be fine for a month or so with little kids, but as you say, its a temporary apartment. But only because I like green. The only hookers there are the ones in business suits.
Check out www.Comparis.ch
We all rely on public transport here. Many families dont have cars, because they dont need them. It might be too far of a stretch if you have always had a car though. Here are some: www.autoscout24.ch
Check out www.sbb.ch
, as to how quickly you can get into the city for work, once you find an appartement or house you like.
Don't be deceived by closeness to the city centre - I live near Baden, and the Baden train takes 15 minutes. People living in Thalwil often spend more time traveling.
Oh - tell your wife to check out the MeetUp.com -there are many mothers groups, and running groups - even reading groups etc in Zurich and around.