I had inquired about that in the past for some friends of ours who have a family of 5. Carnival is the only cruiseline who will let you do 5 to a room...but everyone is right..unless they're really young kids, it would be crowded and bathroom time would be a problem! But they do have those cheaper upper/lower bunk rooms for 2 of your kids if they're older.
5 PEOPLE IN 1 CABIN??? I couldn't even imagine that. Maybe in a suite,even that would be close quarters. You definetly need 2 rooms. UNLESS, you all use the room in shifts>>2 in, 3 out, that would work
The Oceanview Cabins average around 186 sq. ft. It would be very cramped as has been said. I wouldn't recommend it.
We had a group of 5 once and we got one Oceanview with one upper and one Inside Cabin directly across the hall. Looking back, I don't know how we would have stored everyone's luggage in the one cabin. It was hectic enough having two bathrooms and getting ready for dinner.