Since your son is such a cute little guy, I did a quick edit to give you an idea of where I think you should go. Children in the cartoon world, like Pixar, are defined by small little faces with big foreheads (and of course big eyes!).
I think you have a good likeness there. If anything takes away the resemblance it would be the jaw line, you modelled the cheeks more puffed out and the chin too far from the mouth. Your boys ears stick out a little more - but he may appreciate them that way later.
I would probably adjust the eyes a little. Where you have magnified the eyes for the cartoony look you have an edge that runs parallel to the nose, I would angle that out a bit at the top following the real eye shape more and maybe pinch the outer corner a bit as well.
Ran13, Yup - I see where your going with that - I think I’ll play with the shape of the head a little.
LoopyShane - thanks for the input, yes his jawline is a bite off. I’m having trouble with perspective - I think I need to play with the camera focal length some more.