Seriously? I more than happy for his cognitive abilities, reflexes and self esteem, but an adult product doesn't just "contain scenes that might scare children", it is also tested specifically on a mature audience: framerate fluctuations and stutters aren't what doctors recommend for childrens' vision, digestion and assertivity development, and it's a game filled with blue, a color wich tends to increse tension and disturb sleep (I think I can see eyebags in the photo), and then tries to mitigate with a lot of red, but the succession of those colors might induce epilepsy. Also the combat many times tends to make you wait and not attack, meanwhile 5 years old usually smash toy hammers,running outside, kick balls or bump transformers into each other, thus hurting his assertivity again... even if that might be mitigated by the fact that he's already fighting and winning. Many children and teens that he will meet during his life will be at disadvantage due to the fact that he already grasped concepts as dodging and blocking to relate with other beings.
I think he will develop good and well anyway, dad should just bring him to a neurologist to check his sleep