I'm 230 and mid 40's for what is worth... Find a real kayak shop and test paddle a few... see what you like or don't like. Comfort, stability, and ease of paddling general are better with higher end brands. I like an elevated seat and the ability to stand (to stretch). My old Jackson Big Tuna would work well for you, very easy to stand when solo. I took a buddy out in it, combined weight over 500 lbs, we didn't stand but both fished. Big Tuna gives you the option of taking grandson, or going solo. My current boat is faster (easier to paddle long distance, which I do), a Jackson Cuda 14. Also take a look at Wilderness System and Native kayaks. NuCanoe mention earlier, is a good bet also.