As a mom and 9-year resident of Petaluma, I can say that there is not a better community in the Bay Area for raising children. This town's cohesive nature and family-oriented community never cease to amaze me.
Look at www.greatschools.org for school info. 3 of our elementary schools last year scored 10/10 from the State Board of Education.
In terms of affordability, Sonoma County is one of the least expensive ares in the Bay Area and Petaluma still offers convenience to San Francisco commuters. Countywide, Sonoma saw a 16% increase in home prices in 2012 but historically, prices are still near 2003 levels. This, combined with super-low interest rates allows your money to go so much further than it did then.
There is a quality of life in Petaluma which is difficult to match. The warm sunny days and cool nights make for happy people and grapes. There is a contentment and local enthusiasm here which I have never experienced anywhere else.