That depends whether you agree with the parents having the choice of how the money they earned is used. My point is that if we take the money from the children

That depends whether you agree with the parents having the choice of how the money they earned is used. My point is that if we take the money from the children on the grounds that they do not deserve it, we implicitly deny the parents that choice. Which may be what you want. But if you do give them the choice of how to spend what they earn, you must accept that they may choose to spend it on people (or charities, or products etc.) that you consider undeserving.