I completely understand what you say....
This is a family member and a child. I want to be hospitable but at the same time I don't want to adjust the menu for my other 20+ guests to fit one person's food eccentricities. And I don't feel like I should have to. Once a child is in school I feel like he should be polite enough to say no thank you to something he doesn't like. I have made sure that there will be appetizers there that the child eats and none of the other menu is so out of the mainstream that there should be a problem--but I've seen him eat in the past and there are so few things he'll eat...all junk food....