Planning ahead is key for smooth holidays. There's the "I'm going to put a little bit of everything on your plate. Taste it, and ask for seconds of what you like." strategy. There's also the negotiate-in-advance strategy, where your kid tells you which of the available foods are acceptable before you arrive, and you only put those on their plate. Plus, if you prepare your kid's plate, you are able to make sure there are no same colored foods next to each other, or none of the food touches, or whatever your kid's food trigger is.
Great reminder for parents!