I believe that all Category 4 staterooms are the same and that all of them will accomodate 5 people.
They have a queen bed that can be split into two twins.
They have a sofa that converts into a twin bed.
They have a pull down berth located above the sofa that is a twin.
They have a Murphy Bed that pulls down from the wall and is a twin bed.
When you use the sofa as a bed and the pull down berth, the cabin steward will make them up for you and they will be like a bunk bed, with a ladder and railing for the top bunk.
Before anyone can really suggest a particular cabin, you would need to consider what things are important to you that would help narrow down a location. Some things to consider:
Forward
Midship
Aft
close to an elevator or not
easy access to Mickey Pool (aft) or the Spa (forward)
Without knowing any of your preferences, I'd have to take a middle of the road approach and suggest a cabin in the midship area, such as 8x36 to 8x56. Cabins that are in the 8000 range are on the Port side and cabins that are in the 8500 range are on the Starboard side of the ship.
I have stayed in cabin 8026 and we enjoyed it there, the location was just fine for us.
hope that helps