We live aboard a St. Francis 44 cat with our now 6 year old son and a baby on the way. Planning to cruise again when baby is 2.
While we have a separate cabin for our son, he doesn't use it yet. For sleeping we have a big family bed in the master cabin... and he is JUST now starting to hang out in his room for fun every now and again. Basically, boat families are pretty tight knit, and we don't necessarily want to be away from each other. When we do, we go outside.
Even though our boat is big for a family of 3 (soon to be 4) we tend to be in a puppy pile in the same place most times. Just offering a different perspective.
You can see examples of everyday life aboard and the layout in our blog (I think the link is in my sig??)
best of luck to you!