My only point to add is, don't forget the two cruises are totally seperate as far as RCI are concerned, so on the last night of your first cruise, check your bill to make sure its correct...it does not carry over to the next cruise.
As said, in the US, you have to get off the ship to go through Homeland. In Europe you usually just stay on the ship, get your new card given to you (sometimes on the last night), so you can go and explore if you want. In Barcelona, you used to get a card so you could jump the security line to get back on board...don't know if they still do. Also in Barcelona, there is a duty free shop after security, so you could buy a bottle or two and take it on the ship, as they don't have the scanners set up on the ship...just saying!
Simon