So, check the website for your cruise line or call them to find out what their specific requirements are. But beyond that, I think you and your husband need to sit down and talk why you want this so badly and why he has such a problem with it. Does he hate the idea of wearing a suit at all, or just the idea of your mailing a photo of him in a suit to everyone you know? He might feel that makes him look phony. Maybe there's some sort of compromise (e.g., a collared shirt, khaki pants and a sports coat) that works for him, you and your cruise line.
Lesley Carlin has been writing about travel and etiquette professionally for more than 10 years. As one of the Etiquette Grrls, she is the co-author of "Things You Need to Be Told" and "More Things You Need to Be Told" (Berkley). Have a travel etiquette question of your own? E-mail Lesley at email@example.com.