Just curious, what was the other cruise ship you were on and how did they treat his new jeans in the dining room number ? If they didn't hassle him on the other cruise line (which unless it was Windjammer) which probably had the same suggested dress code for after 6 pm...you are going to have a hard time convincing him that he has to wear something else besides jean on the Conquest
Are you prepared not to eat in the dining room for dinner the entire cruise
Are you going with another couple that perhaps the other man can chat with him before hand ?
The dockers suggestion is a good one, buy some dark blue ones
You know us men, we can be set in our ways sometimes (VBG)