Christy, my grandsons were 14, 8 and 2 when Neal passed away. Pop was their idol, mentor and hero. The youngest really does not understand where Pop is. We told him he was in heaven with Jesus, but still to this day when he comes to my house and sees Pop's truck he ask if Pop is here. So he really does not understand.
My other two have just been devastated. I know Hospice has counseling for children as my two oldest went a couple of times. But then they decided they did not want to go anymore. I think the best thing for them is we talk about Pop all the time when they are here. If they seem sad I will sit with them and we cry together and I tell them it is ok to cry. We cry and I let them talk if they want. The oldest one has become a mother hen just like my 2 sons. I have been told that that means they are afraid they are going to loose me also.
I think Christy you just need to talk to him and let him know you love him and that he can cry with you or talk with you or just sit silent with you. You could call Hospice, they have counseling even if you did not use them.
I hope this helps some. It is hard to do when you are grieving also, but I just wait until they leave and loose it then. Hugs