Well since they are starting early I'll tell you why I will never buy for a child from the Angel tree again.
4 years ago I picked a little boys name off the tree. I bought him $100 worth of toys. It was a bunch of small stuff. I found out later from a friend that volunteered there that they did not give that little boy all of his stuff. They split it up among a few different children. That pissed me off. I didn't buy the stuff for multiple kids I bought it all for that little boy and I expected him to get it all. Because of that I will never pick another name off the tree.
EDIT will someone please tell me where I said I wouldn't do charity at all? The angel tree is NOT the only charity in the world.