I would also suggest that you write a short note to Carnival.
Carnival Cruise Lines
3655 NW 87th Avenue
Miami, Fl. 33178-2428
and let them know how wonderful these individuals were.
Not everyone gets the electronic email comment cards....and this is the next best thing to getting these hardworking individuals ther recognition they so deserve.
Put the Ship, Date sailed, Dining Room and Table number.... (and their first names since you have them)