It is, of course, very good. I especially like the light fall off on the background. Was this in your studio or at their house?
It is maybe a tad dark, Mom's face is OK but all that dark hair makes for a lot of dark tones and it looks like the white clothes could use a little bump in brightness. At least that's what I think when I look at it...I would probably go too far and over do it. This probably looks great as a large print.
As for the pose, it is very intimate but I feel like I want to see their eyes. It's good in that it has the feel that this is a 'snapshot of their lives'. (not snapshot in the derogatory way). However, with the lit background and soft studio lighting...it seems odd that they are not looking or posing for the camera.
I'm not sure I'm articulating my point very well. It's a very nice family shot but it just seems like it's missing something that will really hold the viewer's eye. I'm sure they are happy with it...which is what really counts.