When you are taking pictures of your kids (or any people for that matter,) always focus on the eyes. Whatever the psychological reason, eyes are important and when they are sharp in a picture, they really draw you in. This is especially true when you have a shallow depth of field. Look at the difference:
This one is focused on the eyes
And this one is focused around the tip of the nose.
In both pictures, our eyes are drawn to what is in focus. The first picture is much more interesting and much more flattering because the eyes are in focus. Here is another one where the eyes aren't the point of focus.
And here are some with the eyes in focus.
And if you have to choose, the closer eye is usually a better choice.
