Something happened that may or may not have involved children and a crusade, but it's not like someone said "hey let's send a bunch of children!" and then everyone else said "sure, take mine!" (as amusing as that would be, as a parent). It's even possible that the whole story is a myth.

The best place to start is u/sunagainstgold's answer about the Children's Crusade from a couple of years ago:

Is there a consensus among historians whether the 13th century 'children's crusade' actually happened? If it was a myth, do we have any idea where it sprung from, by whom, or why?