What boat (s)?

Got a wife and a 4 year old. Rented a 3 seater before and it was fun but felt slow and hard to turn and the seat was terrible. I think we can squeeze the kid onto a tandem with us. Primary use would be lakes and some spots in the Delta, possibly on SF bay to bag a halibut or stripers on a calm day. Would not always be the 3 of us, me and the kid would likely be primary users. So it would be nice to have a boat that can be easily solo paddled.

Not set on any brand or model, I figure I can screw some rod holders and my fish finder to pretty much anything. Got next weekend free, we might rent a boat from CCK out in Oakland and see how that goes. Definately going to be renting a few before we commit to buy and open to getting a used boat (or two). Looking to keep cost of boat to about a grand, we dont have any other gear so I figure 500 or so will go to paddles and other gear

Here is a great priced double for you and the kid if you are considering two kayaks. Not mine.

https://monterey.craigslist.org/boa/d/pacific-grove-kayak/7517915425.html

there many variables so my advice would be to stick with your plan. Visit a prominent reliable retailer and check out whatever they have. Rent one or two, or as many as you like. Go with the one that is best suited to you, as there will always be compromises.
I've not paddled many doubles, but Ocean kayak and Malibu two's were quite popular rentals when I was at CCK.

My first kayak was a Malibu 2 and I set it up to fish with when my son was pretty young. We've trolled up a lot of kokanee and trout on that kayak. I set it up so that I could use my fish finder from the rear seat or move it to the middle seat when I was solo. The Malibu 2 is very stable but also slow. I've had it in the ocean several times but I would not venture far with it as the combination of length and width can make for a challenging paddle in deteriorating conditions. I'll try to find some pictures to give you an idea of how it's setup.

Malibu 2 is a great boat for taking a young kid out.  It is not a great boat for much else.

Took the kid out to lake chabot and rented a 'feel free corona' tandem. It worked good for just the 2 of us. It had 2 seats mounted, and I noticed in the middle it looked like it had 1 more seat molded into it. Felt pretty stable, easy to maneuver and get around. I think I can make something like that work for us

I have an old Old Town Loon 160T (tandem) sit inside that I used with my kids from under teens through teens.  We'd put 2 or 3 of us in the boat.  Ran it down the rivers, all the local lakes and Tahoe / Fallen Leaf, down the Chetco river out to the ocean, and fishing off the coast.  At one point I added buoyancy balloons to bow and stern.  Great boat, still have it, hoping some day might be some little ones again.

I have a Perception Tribe tandem 13.5 and a Lifetime Spitfire 13. Both are good hulls for family paddling - stable and fast enough, fair amount of deck space, etc. The Lifetime is super stable - I'm not convinced it can be capsized unless it was taking on water. The Perception is fast - I can solo paddle confidently against wind/currents in the bay without much hesitation.

For fishing, the Perception doesn't have very many flat spots, so attacking stuff like tracks/rod holders/etc is a challenge. It does have a center seat though, and paddles well solo. I think it is very similar to the OK and Malibu tandems.

The Lifetime has a lot of flat surfaces, so attaching stuff is easy. It does not have a center seating position, but it is very spacious between the front and rear seats - our dog rides there happily on family paddles. 

With seats - the foam bottom sit on the hull type are pretty much all going to uncomfortable for longer days.  The framed lawn chair style are much better, but most tandems don't have those and the ones that do usually don't have a center seating position.

Lower tier tandems (like mine, haha) usually come with paddles, and they are good enough for family paddling.  I have no complaints with the Lifetime paddles, but for solo fishing trips I prefer a longer, grippier paddle. I have the Cannon fishing paddle from West Marine, and like it a lot. Sturdy, adjustable length and angle, and is pretty grippy.

Lot of good info on this forum, and lots of good people here to help get you setup!