OK, here's my usual plug. Branchburg. Particularly the "Stony Brook" area. check with your realtor. There is a center hall colonial house coming on the market through Weichert (and NO I am NOT a realtor) on Swan Court that would be perfect. Nothing but young families. The homes are about 35 years old, but the whole neighborhood is built on rolling land with trees and views. Great access to 202, 22, 28, 287 and 78 from that area.
You want young kids, you got them. You want Bunkos groups and Moms at the bus-stops? You got that too! And by the way, 5 kids from Somerville high school just went to Cornell this year.