Well I am another newbe to the site but over the time I,ve been boating I have know several families not to just have children onboard but have there child born on board any trouble I have had with kids has been with ones outside the marina coming in throwing stones and generally not respecting boaters life styles. all the kids on boats that I have experianced have had full respect for other boaters and know the dangers better than anyone else.
But you are still stuck with the fact that marina owners have the right to make any rules they like when ever they like.
