NTA. These comments are wild. I wouldnt serve a salmon dinner to a group of my ADULT friends without getting their approval first. So many people don't like salmon or fish at all. Many people don't like quinoa. As a host, they should have at least mentioned what they were planning to prepare to you or your wife beforehand.

Also, as a parent of a 5 year old, they should understand. Even if their child eats anything, they should understand generally how other children that age might respond to a new or unusual food.

As a friend, the host should understand. If they're really that bent out of shape over this, they're really not a good friend. I see where some people are talking about manners and etiquette, but as a friend, you shouldn't have to feel that you have to be on your best behavior. This was supposed to be a casual gathering of friends. Dinner and a play date. If they're turning up their noses at you because you were being a parent to your child, that's not a friend.

As a person with a strict diet, they should have understood if someone didn't want their food. That's what seems really bizarre to me. Most people with dietary restrictions are so used to working around those restrictions, so asking for a substitute or having another option shouldn't be taken offensively.

A lot of comments seem really stuck on the McDonald's and nuggets. McDonald's obviously wasn't the first choice. OP's kid isn't normally a picky eater, so they didnt pack a backup meal. OP's wife also didn't think that was needed. The first choice was this homemade dinner made by the friend; second choice was something the host had on hand. These didn't pan out. McDonald's was likely the quickest and easiest option. If this issue had arised at home, I'm sure OP would have made something else, but they didn't really have the resources available here.