Gosh, this is a tough one to answer. Where about the Central Valley are you guys?
I would say that almost any harbor is a good one to try. Pick the one closest to you guys. BUT, before making the maiden voyage take into consideration a few things.
First, know the tide change, how strong it is, and the wind. Next, avoid parts of the harbor that are dense with boat traffic and sea dogs. Sea dogs don't really do anything to you but just like a dog they'll mess with you if you're too close.
Always know where your buddies are and that they know where you are. When you fish, stay near some kind of structure that you can grab a hold of or beach if your vessel takes a puncture. Don't forget safety, have a life jacket on your tube, whether you choose to wear it is up to you. Some guys have brightly lit clothing worn to stand out and some use a signal flag as a substitute.
As far as tackle goes, I think in the Central Valley you'll encounter rockfish, halibut, croakers, perch, mackerel, and salmon? Not sure about the last one.
I've shore fished Morro bay once before and caught some massive rubberlip perch using shucked mussels on a split shot rig and light 1/8oz dropshot rig. For the rockfish I threw plastic worms on jigheads and T-rigged them. I also threw some small bass jigs that I hopped off the bottom for some success.
I've read that Santa Barbara Harbor has sand bass and some tubers have caught them there. Try there if you're closer to there.