Check out the SF Bay Area!
Half Moon Bay is on the coast about 40 minutes south of San Francisco, 50 minutes north of Santa Cruz. The town itself has plenty to offer as far as activities for children (classes, library, etc). Lots of hiking in the mountains but also along the beach, mild weather all year long, and a great health food store and homeschool community. It's also just about 20 minutes from the SF peninsula which consists of towns such as San Mateo and Palo Alto If you're looking for more rural living you could look into land south of HMB between HMB and Pescadero. All the land around here is pricey compared to other rural area in the country though.
Another N. California town I've recently visited and loved is Fairfax. It's about 40 minutes north of San Francisco in Marin County and is really awesome. It has a great natural food store, restaurants, and is located very close to the bigger town of San Rafael. Very cute town!