I am sorry about your wife I can only hope she gets better, I almost had the same problem last year because of a last minute problem At that time I had the idea: "that maybe you can call Carnival and change your booking so another family member can go with you like your son, a good friend with all the documents needed..."
I like to make a note just for people outside USA,
I am from Puerto Rico and so far the insurance companies that I have call, do not insurance my trip because they don't include my island in their sevices even carnival don't do it, I have already pass my due date and so for me, I have to go cruising hoping nothing happens and is the same case with the carnival credit card you can get nautical miles but it does not work on Puerto Rico.
Just a friendly recomendation:
I consider that Carnival should look this problem because I travel every year on their cruises and I had enjoy each and everyone of them, but I cannot use their nautical miles or cruise insurance, and believe me, I had tried on each one of my cruise and the answer everytime is the same...