October 19, 2008 2:34:22 PM CEST
this response is probably a bit late, you can find out about the demographics of an area on the Funda site when you look at a particular house.
You can click on the tab Buurt, and then find a link on that page called Buurtinformatie
you will find the following information in dutch (i added the english translations)
Gezinssamenstelling (Family composition)
Gezinnen met jonge kinderen (Families with young children)
Middelbaar paar zonder kinderen (middle-aged couple without children)
Jong paar zonder kinderen (young couple without children)
Koopwoningen (Own homes)
Tuin aanwezig (garden present)
etc, you get the idea. you can translate the terms on the page to get an impression of the composition of the neighbourhood.
as for the following places, i have lived in a few of them and know most of theml fairly well.
Rijswijk - a quiet and in some places genteel neighbourhood. many of the areas have a fairly elderly population with not many children. there's a huge shopping mall there, very popular place with many. not much ever happens here (knock on wood)
Voorburg - also a bit of a quiet suburb of the hague, some parts are rather shabby. a lot of renovations and building going on here. generally not a bad place to live.
Leischendam - see voorburg, but there are more newer buildings here. many flats like voorburg, some can be quite ratty. both places would be okay to live but not everywhere. look carefully before you leap.
Wassenaar - the posh neighbourhood of the hague but in the village there are a number of affordable houses. it's nice, very green. upkeep of roads etc excellent. if you can find an affordable place to live here, go for it!
Wateringen - small village, very pretty. far as i know, public transport to the hague is not the best connection in the world.
Delft - i love delft but it is a wildly expensive place to live, many homes are super small and not in the best condition. some parts of delft are really not very nice, walk through a neighbourhood before you choose.
Zoetemeer - not a bad place to live. there are one or two neighbourhoods where i would rather not go with kids, palestein and meerzicht with the mega flats are not cool to live. lots of green in and around zoetermeer. train connection with the hague is pretty good.
if you have kids, you might also consider living in nootdorp - a lovely village close to the hague, it's expanded a lot over the past years. it has a tram connection with the hague and recently got a station as well. pijnacker is also an agragian village that's seen a lot of expansion in the last years, very pretty to live in but here the public transport is not the best connection but it's doable.
you won't ever be far from amenities in the hague region, that's not a worry.
perhaps too much information, i hope some of it is useful to you