A small toy boat that can be towed behind on a string. Be ready to practice MOB drill to pick it up when the string gets loose.
Racing rubber ducks. Yes you have to pick them back up before they get away too far.
Play pick up Dad's hat when it blows overboard.
Riding on the bow with Mom or Dad, given safe conditions. Take turns.
On the tip over thing. The best solution that I have heard about was that lucky boats sometimes have the Troll named Keel living under the boat. The Troll Keel is very strong does not like it when the boat tips, so Keel holds the boat from tipping too far. Sometime kids have to help Keel by letting the jib or main sheet out a bit. Sometimes Keel makes funny growling sounds, but the kids usually catch Dad pushing a button when that happens. It's often good to investigate the bildge to see if Keel is down there. (Disclaimer - not my story - search SA for the Troll named Keel - just love it)