We just got off of the ship in Barcelona, but had a 10:30 flight so baggage was not an issue for us.
However, I seem to recall that the ship had a city tour for people with late flights. As I remember it, the baggage was stored on the tour bus and the last stop was the airport. You might want to check this out to see if this was, in fact, the case.
Of course, this option may preclude shopping except for the duty free at the airport.