Most of the suggestions I have read have been the same. To sum them up:
- Put the kid in a life jacket when underway.
- Devise some kind of toddler harness and tether system when ever kid is above deck.
- Teach them to swim.
- Teach older children to row the dingy. Started by having them practice row with the painter still tied to the boat. As they get better give them more line.
- Put netting up around the life lines.
- Lash a car seat above or below deck.
- Have some kind of playpen area, either a commercial "pack and play," or create one in a bunk with netting or lee cloths.
- Bring things to entertain them like toys and books.
- Let them participate in sailing, steering, etc. But don't push it because it is really not that fun for kids for very long periods of time.
- Find other kids and cruising families. Meet up with them again if possible.
- Hide fun treats and toys to take out for long passages and bad weather.
Carseat flotation
http://www.sailjazz.com/editorial/read/27
Immersion Alarm (LOL)
http://www.weliveonaboat.com/2008/07/keeping-kids-safe-on-a-boat.html
The V-Crib
http://www.searoom.com/sail_baby.htm
Comments by Gaff Cutter family and Hanging Carseat
http://www.ybw.com/forums/showflat.php/Cat/0/Board/pbo/Number/397323/an/0/