All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If this act does not involve painting a living being, and it is not feared that this material used in drawing will harm the faces of these children, then there is nothing wrong with that –Allah willing.
However, if it includes any of these Islamic prohibitions, then it is not permissible.
Drawing living being is forbidden whether the pictures are represented in real form [of the object] or drawn on something.
Ibn Abbas said: "I heard the Prophet saying: “Image-makers will be in Hellfire, for every image they made, Allah will create a soul that will keep on punishing them in Hellfire." Ibn ‘Abbas, may Allah be pleased with him, added “If you must do so, then paint images of trees and inanimate objects.” [Muslim]
Anything that causes harm is Islamically prohibited. Ibn Abbas also narrated that the Prophet said: “There should be no harm nor reciprocal harm.”
Allah knows best.