Concerns of rearing of in-laws child?

I have a 5 year old brother in law, I'm 30. Basically, my wife's parents had a kid when they were old. The child is amazing, but I am concerned over how they are raising him. They shower him with love, but I find it to be more of a grandparent spoiling their grandchild type relationship. He eats anything he wants (mainly junk food). They also seem extremely lax with teaching him things - they don't read to him or do anything education related, he is starting kindergarten and doesn't know his numbers or ABC's. As a former teacher and tutor, I know he is extremely behind for a child his age. I love the kid, but I don't know if it is my place to say/do anything. Simply put, i think they are far too old/tired to be rearing a child of that age. Should i just butt out?