We used a regular car seat. It wedged nicely in the cockpit floor well. (sorry I don't have a picture of this). We had him facing rear, so we could see him and he could see us. I put in some straps on the starboard setee where we could strap down the car seat and this did come in handy during a 20+ knot squall. It seemed like every time the engine was on he'd sleep "like a baby." Maybe it was the carbon monoxide, but it sure worked. We even ran the motor for 20min or so in the evening at anchor just to get him to sleep.
As for a spray hood, I wouldn't think you'd need that. If you have a sun shade on the car seat that should suffice. If the weather is worse than that, I'd mount the little one down below, rear facing, where you can see him/her from the cockpit.