I'm not going to allow my friend's son to come on our trip
What is the reason why his son is not able to join you?
His son is too young for our party. I heard his son was in advance level of maths these days.
I'm sorry, but it's your friend's trip too and he can decide who can and cannot go. It's not nice to dictate who can come or not. He possibly wants his son to make lots of good memories, you shouldn't prevent that.
Shit, I don't care.
Just be careful with making decisions for the kids of other parents. Parents do not really take this very well as they want to be the one making the decisions for their own kin.