He could be by ok. I would incourage him to bring along a sport jacket. He'll probably be glad he did. Maybe he would be more comfortable with a mock turtle neck and a sport jacket. I think the sport jacket will look great in that special picture with the Captain. What do you think?
On the first formal night there is a welcome aboard party before dinner. The pictures are taken with the Captain there. It doesn't matter if it's your first RCCL cruise. I your husband doesn't have a sport jacket don't bother buying one just for that. If he does have one, hide it in you suitcase.