Why not call RCI and speak to their Shore Ex department and they will be able to advise 01932 83432.
We sailed with this cruise company and it was fantastic, but i would not book trips online, we did and due to bad weather before we went trips had to be cancelled it took us 8 months to get our money back, you can book them on the shi.
Book your shore trips on board,but book early (1st full day on board fo popular or limited number trops) and watch weather! You will really enjoy liberty of seas.P.S. Im FROM BELFAST.---Dont worry aabout times---they get it right!