I completely understand that it was an attempt to reclaim Jerusalem. But for what reason would they possibly think sending children to fight a war was a good idea? Was it simply a matter of they lacked enough adults to launch a campaign?
Note: I did a little bit of searching and I couldn't find this question previously asked. If it has been, mods please delete my post or let me know and I'll delete it. Less clutter is better.
You seem to misunderstand the children's Crusade. It wasn't anything that the Church planned or even any nobility. Instead it resulted from two young lads who claimed to have visions from God saying that their peacefully convert the Muslims in the holy land. They managed to gain a small cult of some thousand kids. Not to make this simple but it led to a many of the youth being sold into slavery