You are exactly where I was this time last year. I had resisted a dog in the family, feeling it would not work with our sailing and travelling lifestyle. We had a good gig going, as my sister lived a block away. She had a dog and we dog sat regularly, so I was able to convince the kids that the dog was "ours" too.
Then my sister relocated and I was hosed.
That's when the pressure really started building. Not just from the kids. My wife, too. I was outnumbered and outgunned.
Late last spring, we brought a Miniature Labradoodle puppy home from a breeder out in the countryside. I think it was the happiest day of my kids' lives. I kind of felt like a schmuck for holding out so long.
We chose this breed for a couple reasons. First, they are water dogs, with webbed feet. So they are strong swimmers. Also, they are low/no shed dogs because they have hair instead of fur. That is not to say they don't lose hair -- but they certainly don't blow their coats like most furred dogs. And they need to go to the groomer for a trim every 3-5 months or so.
Another reason we chose this breed is because several folks at our marina have them, and we'd had the chance to interact with and observe them around people/kids, boats, and docks/water, where they appeared perfectly at home and at ease.
The Miniature Labradoodle is a cross between a Lab and a Miniature Poodle, so they are not as large as the Labradoodles you might have seen. Our gal will be one year old tomorrow, and she is about 35 lbs. I can still pick her up one-handed and set her aboard from the dinghy.
Despite my initial reservations, I now have to admit that she is really no problem aboard the boat. She really took to it quickly, being very nimble on her feet (like a poodle) and fairly easy going like a lab. She is very content to lay about above or belowdecks, or cruise around in the dinghy with the kids.
Whatever breed you choose, I think you'll find it's not as much of a problem as you feared. I know I did. And our kids are so happy to have their "very own" puppy. The joy they get from this dog alone makes it worth it.
Sorry, I hope folks won't mind a few photos of our expensive mutt -- her Sailnet debut. Gosh, they grow up so fast