Our next trip will be the first time as an "adult" for me son (he'll be 12, and we were last able to go at 9). He is picky, he doesn't like sauces, has difficulty with some textures and prefers certain foods. He will try new things, but if I don't think he will actually like it I prefer to do that at home rather than paying full price for a meal he'll take a bite of and waste. I suspect we will do more quick service where we may order kids meals rather than sit down places simply because of that. We do look at the menus, and it helps if there are pictures of the food to see. He prefers pasta plain, meat with no sauces, raw vegetables (but not salad). He is well aware that he is "picky" and does try to want to try new things. He likes when we cruise because he can try new things and have a back up of something he knows he likes. And as for junk, yes, in public that's probably the safest choice for my son, restaurants like to offer "fancy" foods with sauces and such, he just wants things plain. But chicken nuggets and pizza are usually universal. At home though, he likes all kinds of meat and seafood, with raw vegetables (including broccoli).
As for the OP's original question, I'd look at the menus and see if there is something your son would eat, and if not, don't plan to eat there. I'm going through this now, and we are looking at menus together to see what it offers, the problem (of sorts) being that even the buffets we used to go to are now family style with a set offering, most likely that he won't eat. So breakfast is a top choice and any place that will serve steak, plain. Good luck, and enjoy your trip.