I would get at least 2 rooms. Depending on what ship you are on, the royal suite may only sleep 5. Also depending on who will sleep with whom, and if everyone needs a separate bed, etc. You in essence have 6 full sized people and many of the fold down beds are not that big. If the 4 adults are a pair of couples and can sleep together, I would get 2 rooms. The adults can sleep in the queen bed and you can have 1 teen in each room on the sleeper sofa. And you can do that with concierge rooms if you want.