I think the counsellor at school is a fantastic plan of action. They will have a good idea on how to help children get through grief. Often having something like a photo or something is perfect to give them something to hold onto, also telling him how you have gone through the grief yourself.

I am not someone who has done counselling, but one who has been through death as a young girl and young adult. I found that when my family were most able to say "You know, I don't know... this sucks" was when I felt like it was more real and okay to feel that way as well. not an easy thing to go through, or to watch your child go through as well.