We only have 2 kids, but I have known people with 3 kids who went with family members and put one of the kids in with Grandma and Grandpa.
The other alternative I have heard is to put Mom in one Cat. 10 and Dad in the other Cat. 10 room that adjoin to each other and then put 2 kids in one and one kid in the other. Then when one board just leave the connecting rooms open and you have a 2 room / 2 bath suite.
Again, I haven't done this since we only need room for 4 of us, but that is what I have heard of other people doing when there are 5 or more in the family.
DJ