Re: First year taking son out on boat
I had my son out at 3 months, 1 year and plan on having him out again this year when he'll be 2+ years.
Shade is definitely key so put up those convertible tops/bimini's. First time out, my son was in the sun, and had an uncomfortable (for him) life jacket on. We made it maybe 20ft from the dock before I had to turn around.
Last year was much better as we bought a neoprene life jacket for him instead of the infant horsecollar. I'd recommend anyone buying a life jacket for a munchkin look into the neoprene as they're much more skin & kid friendly. He was also a little more adventuresome on the boat this time around as he helped supervise cleaning it in the spring and when family vacation rolled around, he went on his ride he walked from mommy in the back seat up to the front seat with me, climbed up on my lap and promptly fell asleep...which is what us parents wanted

I'm sure this year will be even better!!
I can't echo the other comments enough - bring food, toys, drinks, whatever keeps your child happy along with you as it will make YOUR experience all the better. Nothing worse than a miserable munchkin!
Ohh yeah and speed - all the infants/toddlers I've been around absolutely love idle or just above idle. It won't scare them and the humming/drumming of the engine put 90% of them asleep....which depending on how your day is going might be the thing you're looking for!
**This wasn't my first rodeo with infants on board as I have done the same for my cousin's youngsters so I had a general idea going in.