Charlie,
They boat I got is a smaller for a 3 person at 14' long. It's quite wide so should be as roomy as most 15'-16' models. Stealthcraft makes some 12' & 13' models as well. If it's primarily you and the pooch or you and one other person, the 12' boat should work nicely. With that said, where you're fishing a raft might be a better choice. If it's shallow / fast water where you're going to bounce off rocks all the time, a raft will be a lot less maintenance than a hard boat. The downside I see with a raft is you've got just as much stuff to tangle on as you have in a toon and there no built in storage for rods .