A canoe would be good for cruising but transporting it sounds like a nightmare. I've never been on one. Aren't they extremely heavy? I'm the one on the kayak who paddles for like 30 seconds then stops to enjoy the view.
One canoe is lighter and easier to haul than 2 kayaks. And a canoe is much nicer for the kind of laid back paddling you describe. More stable, more room for stuff like coolers, sun shelters, and camera equipment. The lighter ones are more expensive though, it would be an investment so you need to think about how often you use it and what the recreation is worth to you.
Canoes aren't that heavy. I did some portaging on a week long trip, and with two people it's pretty easy - flip it up and carry on your shoulders. (One person can do it from the center, but it's a pain/can't se etc.) That said, it's really a two-person paddling endeavor (though I know someone that would go out with his dog for ballast. Worked fine till the time the dog got really excited and ran back to him). Since you say "Preferably something for two people that is not unwieldy for one person to take out themselves", I'd say that crosses off a canoe though.
I have a sea kayak. You can really fit more in than you expect - I've done a 10 day sea kayaking camping trip with friends just fine. While I mostly carry with two, it's easy enough to pop on my shoulder and carry by myself although I imagine an older person would have trouble. My 65+ yo parents carry with two just fine. I'd recommend plastic. A friend has a carbon fiber one, which is crazy light and totally unnecessary in most cases. (He had leg cancer, so this allowed him to still transport his own boat.) Once you learn to load it, it's pretty fast to put it up and take it down. Get a used one and you'll get a deal plus be less worried about someone stealing it. It does add wind resistance and thus to your gas bill though.
Putting in a plug to please don't get a sit on top. They're not nearly as responsive to maneuver. You get wet. Harder to transport things.
Consider also taking a lesson on paddling so you learn to use your back and not your arms. You're much more energy-efficient so you won't mind paddling on your so much at the end of the day. :) (For a short lesson: Separate your hands on the paddle so when the paddle is on your head, your arms make an L. Most people paddle with their hands too close together. Next, envision a giant beach ball in front of you. Now paddle around it, keeping your arms generally straight. This means paddling further out in front of you than you would likely otherwise do, and turning your upper body somewhat with each stroke, so you are powering it from your body and not your arms.)
