The issue can be really tricky here. I have had many dealings with Child Protective Services. If they are called, they will come interview your grandson and review the home situation and possibly interview the parents. They may possibly remove the child from the home if they feel that he is in danger. The most logical place for him to be placed would be in your home.
However, you can call Child Protective Services anonymously and ask them if a child is removed from the home and there is a willing grandparent to care for the child, would that be possible and under what circumstances.
You are not the your son's legal guardian so you really cannot go to court because the parents are still in his life and make decisions for his well being.
I would call Child Protective Services and they can give you so much advice as to which direction to take. If you need to file a report, which centers around neglect, then do so. You are only protecting your grandson.
I hope that this has helped. If so, please ACCEPT so that I may be paid for my efforts. If you have further questions, please feel free to request Erica.13. Thank you and have a great evening!!!