@Anotherhill
I disagree with the majority. If Adam is there as a child of family friends who were invited, then it’s perfectly fine to sing happy birthday to him too if it’s his birthday as well. I think it’d be odd not to. After all, if it was an adults birthday on the same day, wouldn’t you do a quick happy birthday to them after your daughter?
No.
But Adam is not even DDs friend - he's a 12 yo boy tagging into an ?8 year old girls own birthday party with his invited sister - that’s already DD “being nice” to feed him.
The original arrangement was DD then went with Adams sister to his birthday icecream party afterwards as Convenience for Adam’s mum and for Adams sister.
Adams family can afford a birthday party for him- he’s cancelled his own party as he wants the money instead for a games console for himself.
(It is nowhere near the same - as suggested by another Pp- as an adult’s family anniversary or big birthday party including a younger niece with a birthday too, as all the family are together in a cute way IF the adult themselves suggested it. )
I don’t know anyone who would interrupt a primary school aged child’s pizza birthday party to sing happy birthday WITH ANOTHER CAKE!! for an adult like you’ve suggested- don’t forget CF mum wants to bring out Adams birthday cake too!
I doubt DD wanted him to come anyway. Why should she be told to "be nice" - he’s not even her friend. It’s nice he’s been allowed to come along and he could easily have his own birthday cake at home with OP & DD popping by later to sing if CF mum wants more of a fuss made of him.
The only time my younger DC had 4 year older DC (age 12+!) at those ages was because they came as a friend of my child’s older siblings or that they were special friend of birthday DD who wanted them there. Not as a replacement for a random’s also birthday party.