Depends on what cruise line you are going on. DH and I cruise on Carnival. 1st night is "come as you are" as a lot of times all the luggage has not been delivered to all the cabins yet. So no holes barred in the dining room that night (except NO bathing suits). The other nights, men don't "have" to wear coats and ties. DH wears dress pants, khakis, even nice jeans or shorts with polo type shirts. I wear pants or capris. For dress up night, DH does wear a tie.
Enjoy your cruise. You will have to give us a review once you're back. Sandy