I have a 16 month old boy who's spent a fair amount of time aboard the Searider. I strap his stroller down securely in the bow. It's a reclining type with a sunshade, so he can lie back, relax and mostly be out of the sun. Wife insists that he wear life jacket and be strapped into the stroller. He usually falls asleep that way for most of the ride. When he wakes up and gets restless, he rides on the jockey in front of me. Or if we're just bobbing about, I'll let him walk around, only keeping him away from the external fuel tanks. He can't even see over the tubes, so I'm not worried about him falling overboard!
Yes, if if something catastrophic were to happen, he's attached to the boat, but I consider that an extremely small risk, after 39 years of boating myself. Particularly in comparison to the risk of injury from being thrown about in the boat.