Please do not hesitate about taking your dog with you on weekend trips, etc. Having been onboard with everything from cockers to labs to old english sheepdogs (and cats), please don''t let your fears get in the way.
Labs are water dogs, yes, but - they (like us) have no idea how to get back on a boat without being shown, so teach your pup early, either how to come to the transom to get lifted up, or how to come to a swim ladder
you install (and with kids, a swim ladder
is a great idea anyway). At least while it is a pup, keep a life jacket on him or her. Yes, they can swim, but not forever. I myself have dived overboard to retrieve an exuberant spaniel.
Bottomline is, teach your pup (whether a lab or a yorkie or spaniel(my fav - can you tell?) to come to the boat where he or she can get back aboard (like you would your kids - and a ladder
will help). I have watched many liveaboard dogs swim back and forth in marinas for exercise, but they always knew which boats they could go to to get out of the water.
Try to find your dream girl (or guy) at a shelter.
If not, besides labs, (and I had many labs and shepherds and Malinois myself growing up) please look into Portuguese water dogs and Newfoundlands, in addition to a lab. They have a much stronger water instinct and water rescue instinct than even labs do (believe it or not). A Portuguese water dog may be a delightful addition to your family, if you can afford it. And especially if you do plan on doing a lot of sailing with your kids. They are so at home in the water, hold up much better swimming even when pups, and have a natural protective instinct, which your kids would benefit from in and out of the water. But, they are playful clowns at home on land, too. So are Newfoundlands, but they are much bigger dogs, and harder to keep due to their size.
Hope this helps. Don''t think that Labs are the only breed of dog that are kid friendly and great water dogs. Consider the Portuguese water dog.