We booked a family oceanview on Royal Caribbean. It has a seperate room with 2 bunk beds.The bunk room was tiny, but it was perfect for them. It opened out into a large living room. Then there was a curtain that closed side to side with a queen bed for us.It gave us plenty of privacy, two large windows facing the bow. There was only one bathroom, but it had the best of both worlds for us. These cabins are limited in number,but I'm sure your agent could find you one.
I love the water park idea, but most of the ships have some water slides in the children's area.
If you do the penthouse on your first cruise, it will spoil you for everything else...unless of course money is no object.