PSA: You know, using the word "manchildren" is incredibly sexist. The primary means of manipulating men, throughout history, is from outside forces claiming to be the ones who determine when someone is officially "a man." Whether it's encouraging people to join the military, whether it's a hunting ritual where you have to kill an animal, or any other form of masculine action or desired outcome, the effect is the same. It's denying the innate humanity of men, and claiming that if they don't act a way you don't approve of, they aren't "really" men.
How would it play out if we all tried to determine how women should act to "really" be considered women?
So if you actually care about issues like sexism and equality, manchildren is a pretty insulting term, rooted in the primary type of sexism leveled at men throughout history - and you should probably stop using it.