Selective colouring can work [in very rare cases] when used correctly. It's purpose is to draw the eye to a particular element, for example: If you were producing an advertising shot for a cereal company, you might destaturate the image, but leave the cereal box in full colour. For an infant's portrait, I would think that you would want people to see the whole child, not just his or her eyes. As well, consider matching the child's position to the camera's orientation so that we see more child and less pillor (or whatever that is behind him/her).