Nice Shot, James.
I've taken many a baby/child portrait, and IMHO the secret of a good one is capturing a moment. A laugh, smile or even tears!
My issue with this portrait is not the composition, or the lack of catch light in the eyes, (both of which are forgivable) but the fact that the image doesn't really capture a moment. The image doesn't tell me anything about their personality.
The only way you will do this is to take more pictures. Take your ISO as high as you reasonably can, set your aperture to around f8 and choose as short an exposure you can. Follow the child around the house, taking lots (and lots) of images, and after about 500 frames, you will get a 'moment'.
A nice, well executed shot though. I am sure the parents were very happy with it.
Sid.