We had an owners suite and an inside. The inside cabins are approx. 119 sq ft., and do not have a lot of storage. The owners suite was of course very nice, but a lot of wasted space. The couch was a full size queen sofa, that would be ideal.
Perhaps you may want to look for a jr. suite.
It depends what ship you are on as to size. Some have a pullman for the third person, and some have a sofa bed. Personally for 3 adults, I would go for the sofa bed so someone doesn't have to climb up and sleep above someone else.
The Voyager class ships offer a very limited number of "large oceanview" cabins. These are only located at the very front and back of the ship. Only about 6 per deck so you need to grab them early. These cabins are bigger than the cabins with balancies. In place of a balcony, you get additional floor room. We had one with our 2 long legged teenagers last week on the Mariner and we really appreciated the extra space. I didn't feel that we were tripping over each other. The only thing is that 2 will need to sleep in the queen bed. If that's a problem, then this cabin category may not be for you.
Hope that helps
Mariner of the Seas 6/2006
Sovereign of the Seas 7/2003
It is hard to answer without knowing what ship you will be sailing, but our experience with RCI has been: the cabins are not as large as some of the other lines. The configuration will either be a bunk situation plus another bed or 2 twins and a pull out couch. 3 can survive and have a good time, just don't expect to have lots of room to move around. NMNita