Ok, here's my $0.11 .....
First of all, you've done really well. You have great saturation and wb, focus ... the whole box and dice.
Well, almost.
I don't like the deep black backgrounds here, as they tend to make the subject matter appear as if it's floating in space. By using solid deep blacks, you've not given the images anything to anchor too, and while the surreal effect may suit some images, I'm not sure if child portraiture falls into that category.
Trevor has highlighted the issues with the use of wide angle glass. portraiture is best shot with a slightly long lens ... 85mm-105mm on a crop body tends to give very pleasing results. Of course, to use a lens of that focal length, you need to have some physical depth within the shooting environment.
Which brings me to the next point: you mention the apparent power of the lights, and that you need to stop down more that you were wanting to in order to shoot these images. Remember that if you move the lights further away from the subject, the intensity of the light hitting the subject will decrease. Double the distance between your light and the subject, and you'll only have a quarter of the original power available; if you have the physical space, that can work.
Or you can increase the distance the light needs to travel without relocating them: if you're shooting into a soft box, turn the light around so it faces away from the subject, and then point it into a reflective brolly.
And do pay attention to the placement of your lights. Suren (I think) mentioned catchlights, which are important, but so too are the shadows as and how they fall. Look at image #1, for instance. The lower part of the face is in somewhat deep shadows. Relocating the lights slightly so that they are closer to the axis of the camera's lens might help to alleviate this issue, but this again brings me back to your choice of the black background: here it may also be acting as a subtractor in terms of the light hitting your subject, and thus it may be helping to create those shadows. This is noticeable in images #1 and #3, and especially in #2.
A reflector could also be put to good use here, but if you're going to use a wall as a reflector, do pay attention to the wall's colour. A green wall will do wonders for your son's complexion.