The farther out you get from San Francisco
the more likely you are to find a marina with a shorter waiting list. The government
on the bay to a maximum of 10% liveaboards, and many marinas keep that number at 0%. Expect to pay $200-250 extra as a liveaboard "fee".
We scouted things out about 6 months in advance, visiting every marina in the general area where we wanted to be, and talking to each harbormaster. Take your boat paperwork with pictures of the exterior of the boat. Harbormasters love it when you have it all together. Check back every few months.
It'll be an order of magnitude harder since you don't already have the boat. And with kids
it will also be more difficult as no marina wants that liability (though it helps if the kids have been around boats, members of a yacht club, or something like the Sea Scouts).
Slips are available if you are open to area and have the time to do the footwork (walk-in seems to work best). We spent 10 months farther from my work than we really wanted to be, until a slip opened up closer.
The size of your boat will, to a degree, dictate your success. Some marinas have a minimum size for liveaboard, yet bigger slips are harder to find. Finding a berth for our 21' beam really limited our options.