I would do the same thing too. I feel your pain; I have a picky-eater too! I make sure I talk to the host what’s cooking for the meal and I would request them to make at least one item that my kid would eat. Or I would go in the kitchen and help them for a while and include the dish in the menu. If the relative is not too co-operative, then I would just go ahead and make myself. For me, my kid’s meal is definitely important. You were not at all rude.