Hi D.
I just moved to Northbrook last summer, but it was from another suburb in Chicago (Evanston), so I knew a little bit about it first.
So far we love it. The schools are spectacular, and your kids are going to be attending the best one. District 28 is the 'best district' according to everyone I've talked to, even moms from other districts. Our kids will be going to Meadowbrook, too, but not for a while (they are only 2).
So if you're in District 28, you're probably living in the nicest 'area' of Northbrook, too. Not that there are any bad areas, it's just nice to be closer to 'downtown'. Its a small downtown -- great park.
I don't know much about the after school programming, but check out the Northbrook website http://www.northbrook.il.us/index.asp or http://www.northbrook.info/index.php And check out the northbrook park district http://www.nbparks.org/index.html
Maybe you can still get your kids into one of the camps this summer -- probably a good way to meet people, too.
Good luck! Email me if you have any more questions!
A.