It will depend on his "picky" taste. Yes vegetarians and special diet clients can ask in advance for a menu or options to suit their needs, but "picky" is different.
I would speak in advance of first night dining to the Maitre'D ask him to make your table staff aware of the situation and explain the scenario, explain to him/her what he likes as a basic and get what options are available to him. Explain it properly and they will make it work for all of you in the dining room.
I can appreciate the problem if you are on dialysis. Like any treatment some things appeal and others dont when you want to eat. But sort this out as soon as you get onboard and you will all have a pleasant dining experience.
Put it this way if he wants two poached eggs on toast every night, then thats what he will get
Have a good one