My MIL has invited a family from the UK to my house for lunch on Good Friday. They have a kid about 5 and another about 10. We have a 13 month old ds.
MIL called to see if their was anything she could bring and I said that it was okay I was just going to make sandwiches and hot cross buns. Anyway she starts giving me this big tale about how the boys only eat dry bread, plain pasta, drink 3 glasses of milk each and are really fussy. I said they could either pick apart what I offered and take the bits they like, or they could bring their own food. I have just spent 7 months feeding my ds food without eggs, milk, banana, red fruit, sultanas and about a million other things because he has allergic reactions to them and I refuse to pander to some kids who just don't like stuff.
Anyway it's been left that MIL will bring their "special" food and a gallon of milk and I will feed everyone else. But I did wonder what you would expect your older kids to do when at someone else's house. I only have experience of toddlers.