First of all did he use a TA. If so call them and ask for help.
If he didn't use a TA. Call RCL and ask for help your self. You will need the booking number.
Do it quick. You cruise soon.
Also If you have no luck ahead of the cruise. As soon as you board go to the the dining room and locate the Maitre D and beg politely to be assisted in your plight. They will try to help you if at all possible. There will likely be a line up of folks with issues. Be first if you can.
If everything fails. You will still have the option of eating in the buffet. Not the greatest I guess but depending on the ages maybe the kids can be fed first ?..... passed off to the activities crew and adults eat in peace? Or a combination of options. Good Luck.