a very nice shot, although I agree about needing more DOF. (its a personal preference of mine)
the common misconception is that you need a large aperture to render the background blurred. the truth is that depth of field is just that, a "field" of focus that you can acutally position your subject in. for instance, you can use a smaller aperture, say f4 or f5.6 and simply stand farther away from the subject (if possible of course) you can place the subject in the back portion of the field which will render more of the foreground in focus, and simply crop out the foreground. this will make your entire subject in focus while leaving the background blurred. alternatively, you might have had enough DOF to have gotten the kids head in focus by simply moving forward a little more and pushing the field of focus back some.
plenty of DOF calculators online and as apps for your phone that will show you the DOF when given focal length and aperture.
as for the shot itself, the lighting is good, focus is good, and the pose is good.
a keeper for sure.