There's a small dutch community in BsAs, they get together in "Van Koning", the pub mentioned in the post above. You can contact the dutch embassy which is located @ puerto madero (next to the hilton). I'm Dutch myself, but since I'm not currently living in BsAs I'm afraid I can't really help you with local issues. Feel free to send me PM though, in case you have some questions.
Just returned from warm BsAs to the Netherlands, where we experienced a chilling minus twenty degrees Centigrade last night... Quite a blow following the last four months in BsAs... On the upside: lots of ice skating on ponds and little streams
Check the Dutch Expat Organization (http://www.nedver.org/) for useful info, contacts, and -of course- the monthly meetings at 'van Koning' (every first Wednesday of the month as from 20:00; usually 20-40 Dutchies attending; you will likely run into Dutch students that may be interested in teaching Spanish your kids).
Myself (Dutch), I will be returning to BsAs, albeit likely around March.
Succes en groeten,