San Diego has the zoo and seaworld....both would work with your kids. Monterey has a top notch aquarium. There s also legoland nd Disney land.

Staying in southern California woul limit your driving.

You could o shorter trip instead of up to San Fran you could go to Santa Barbara, solvang, Santa ynez valley then up to San Luis obispo ( Morro bay, pismo beach) then come back.

In flying since you are in Toronto area look at fares from buffalo. Don't just look at flying into LAX, look at Long beach, orange ountry, or San Diego. buffalo has southwest and jet blue.

With your kids ages it may be good to break up the trip with a layover instead of a direct 5 hr flight.

Just did a quick search it looks like San Diego may be the cheaper option o fly into.