The way that children look straight forward to the camera makes the expression more realistic on the picture. He took medium shots and the way he blurred the background, bring forward the person. He did a very good job on framing, because nothing becomes lost on the picture and the make the viewer to focus in the middle. I see that he is really successful to control and manipulate light correctly in order to get the best texture, and the vibrancy of color.
Shallow depth of field is a good tool to have when the background is busy and would be distracting from the subject.