We are both rank beginners at paddling, however-- I've paddled plastic whitewater kayaks in non-challenging conditions a few times, but neither of us has any ocean experience at all, at least not yet.

Mike-
You've gotten some excellent advice already.
Welcome to the forum; yes, you came to the right place to ask your questions!

I love to build stuff, especially stuff that floats! When my wife and I got interested in sea kayaking, we took a very basic 'rescue lesson' from a friend and started padding with a group of friends, accompanied by an expert 'babysitter' on each outing. I immediately started building a kayak for myself. A boat purchase followed for my wife. And, I built another kayak.

Looking back, I feel that approach was a mistake. For non-paddling (health&medical) reasons, we didn't use the kayaks for 7-8 years after that first 18 months of enthusiasm. When we got interested in paddling kayaks again, we took a very different approach, and that is the one I'd recommend to you.

We allocated a good chunk of money to taking a few 'holidays' which involved professional instruction by day and staying in a warm room with shower by night. We learned a lot of skills, paddled a bunch of different boats, realized we needed to focus on proper clothing for our area (dry suits= $$), etc etc. (School was BodyBoatBlade, BTW.) We joined the local sea kayak club and took more clinics & participated in group paddles.

The kayak I built after that was a far better boat, and better suited to my new skills as well.

Knowing what you are doing on the water goes a long way to reducing anxiety when 'out there'.

Neither of us is interested in getting a double - too heavy to load on top of our car and to carry.
Something we both dislike - a lot - is the 'paddling a bathtub' feeling in a wide and deep boat, and most doubles we sat in gave us that feeling.
There an also be issues with difficulty in rescues / flotation if you have the 'wrong' boat. I recall some accounts in 'Deep Trouble' addressed this, but I may be mistaken.

Friends who were looking for a double (there are lots of used ones around (!!) ) grouped them into two classes:
boats which required synchronized paddling, and those that didn't. After that came the weight/price, etc issues.