Other than applications that can have recorded actions or is scriptable, I don't know of any automated means of cutting out the images. Even then, they would need reviewed carefully.

Depending upon the quality of the green screen shots, the contrast of the subjects against it, I wouldn't think in an image editing application it is more than a minute or two per image doing it manually, though.

Because this is an image of a child, if it is a real child involved in the project and not a stock photo, I would encourage the removal of the present image and obscure the face.