Hi Maia,
the cruise lines usually pay some kind of compensation, often in conjunction with a rebate on a future cruise. You or your parents might want to give RCL a call to inquire about this. A special service desk has been set up for "Infinity" passengers. The number is 1-888-701-7192.
Sorry that your parents experienced those problems on their cruise, but I hope they have been able to enjoy the trip, nonetheless.
Best regards,
Raoul Fiebig
Das Ruderhaus