It depends on who else is in the room, etc. What will happen is not a cancel and rebook, BUT....
if it is just 2 of them in the room and you cancel one, the other will pay a single person supplement. You will get back little on this situation--you would be entitled to the amount paid less the deposit, but then the first person fare would double, effectively using up the savings! OUCH!
If there are 3 in the room and you cancel 1, the number 3 person will move up to the number 2 slot and pay full adult fare regardless of age. You would get back the third person fare less the deposit paid on the husband.
Another option is to invite someone else to cruise. You can do a name change on a reservation for very little--it used to be at no charge up to 30 days, then $50 but someone posted last night that it was $75. Not sure which is accurate.
Bottom line--no, it is not a cancel and rebook as long as one adult remains in the room from the original booking. The amount of the refund would vary based on numbers in the room.