If you have kids and need areas of good schools, then your choices are Pleasanton, San Ramon, Castro Valley and Fremont.
As far as being close to SFO, Fremont (Zip Code 94555) and Castro Valley are better choices since they are close to the Dumbarton and San Mateo Bridges respectively.
I used to live in Castro Valley for several years and it is a great city.The weather is good and there is plenty of family orientated events going on in the city. In your price range, you can focus on Palomares Hills and Five Canyons. We lived in Five Canyons and the homes there wer built built between 1995-2001.My children went to the schools in Castro Valley and we were very happy with the schools.
If you need any more information about any of these cities mentioned above, I would be happy to answer your questions.