Good activities our kids like underway: Coloring books
, play-dough, board games like Chutes and Ladders, building blocks, tickle wars, reading books
, and Disney movies. Also topside: making a mess out of the sheets/inhaul/outhaul and then undoing the mess they made, playing with the binos (NOT Daddy's though!), waving to everyone within eyesight, cleaning
the boat, practicing "boat words" and anything related to fishing
Our kids are 2 1/2 (boy) and 4 (girl), and they haven't fully gotten into the cool things we see while underway. They think the whales/seals/porpoises are neat, but there is no wow factor for them (the play-dough is just as cool, and macaroni and cheese beats a whale any day of the week!). Not sure if they don't realize how neat these things are because they always see them, or if they aren't old enough yet to enjoy them. I think the latter.
MOST of the time, if you tell them something is really fun, they'll buy off on it and like it, too! Our kids have never said anything negative about the boat so far. We don't go crazy out there, either, though. We only sail on very short trips with no overnight sailing, stopping at "fun" places whenever possible. I think that it would be tough to overnight sail with just two adults and two kids our age. It would be for us, anyway. Usually we go on a kayak
ride after anchoring
, and try to visit land where we are so they can burn energy. My opinion is you have to be realistic about what you are trying to do with little kids and above all else you have to keep it fun!!