This is a common question and really tough to answer because it varies by even streets in a given neighborhood. While Westpark does have quite a few families, many are older kids (JHS/HS age) and you'll see a variance from street to street.
Places like Woodbridge are hit and miss since it is one of the older neighborhoods and some areas will have a higher concentration than others.
The best bet (IMO) is the newer neighborhoods because families tend to move into them as move up or first homes. Places like Woodbury, Northpark II, Quail Hill and Columbus Grove which have been built in the last 5 years should warrant some looking into.
It also depends on your housing requirements as some places are more expensive (much more than others) or may not have the right type of home for you. West Irvine is also a nice family neighborhood (a few posters on this site can attest to that).
EDIT: Argh... ninja'd by IR2!