Well, we took him. Fully outfittend in a dry suit! He swam,,,, a few, and got humbled. He was really excited though, and had a good time. He is now very determined and amped for the sport.
It probably was too much, which i had suspected, but he was a relentless eager beaver, so we took him.
Thanks for all the advice. We had some good play though, great day on the ol'river.