The problem with well thought out questions is - well there's just too much to answer.
I've never slept at the Old Mill, I've just been in the restaurant. I heard from a couple of people it is descent. It is waaay deep in the bay - you'd probably be better off just staying there and driving to launch someplace else. That whole area can hold game fish - your best bet is to talk to the locals / pangeros right at the Old Mill or at Don Eddie's, right around the corner. There's many more sportfishing gigs down there, they are all close by.
Surf can be nasty down there, you need to be careful. Not sure if I would recommend it if you guys don't have much experience. Hiring panga to take you out may be something to consider - they know the spots, they know where the bite is hot. You won't have to worry about the surf - they'll take your kayaks on board.
SQ Bay and that whole area is supposedly halibut heaven. I personally never caught a halibut down there. WSB is the main game - this season has been real good, and it's still (supposedly) going on. Yellows can be caught there too. You'll have a lot of other aux catch when the bite is good (bass, cudas, bonito, tomcod, rockfish).
Good luck and stay safe.
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