If that is how you feel, I would strongly reccommend not taking your kids boating.
You are right, just because it has been done does not make it safe. I also think that anyone who feels that boating with children is as safe as keeping their kids in a traditional home environment is just kidding themselves. I also dont buy the argument that they could get killed on land just as easy. It is not just as easy, but very possible.
Now, all that being said, you have to ask yourself why? Why take them out there? Is it for your dreams? Well, there is always a self-serving piece to it, I guess. But I think it is to show them a world that is beyond the grasp of most adults and even more children. It is to show them THE aspect of humanity, nature and the world that cannot be seen through a television, week long trips on a cruise ship, or the National Geographic. Cruising is a lifestyle, and a very expensive one. But I would take my child cruising every day of their life versus raising them in some suberb of some city in some house out of sight of nature and the world we live in.
It is up to each parent to make that decision, though. A child cannot make it. Most parents choose the path you have seemed to portray. Is that path wrong? No. I don't think so. Unless you are committed to boating and all of the positives and negatives it can induce, it is not the right decision. But for many parents, they feel that which can be gained outweighs that which could be lost. I am the latter - and support and encourage anyone else with kids that wants to come along.
We will see you there...