I am a Mortgage Broker and I work the entire bay area. My sense is that for $450,000 Brentwood should be considered. It is a way out, hot but windy in the summer, safe, good access to recreation, especially water.
I don't know about the schools. If you need help, please e-mail me.
Alameda is a fine place, but $450,000 won't get you much.
Concord/Pleasant Hill and Martinez would be another option.