Great that your youngest son is trying his hand at portraiture. Not easy, as there is so much to think about, let alone getting the sitters to pose the way he wants. Those who practice the art are much better qualified than I to give advice so I will just restrict myself to saying I like the black and white one best. One of the joys of digital photography is that taking photos is virtually free so he can take lots of shots and then sit down with them on the computer and try and decide what works and what doesn't and, importantly, why
the good ones work.