A similar tragedy happened to a close family friend several years ago.
At the funeral the talks were some of the most memorable I have heard. The family talked about the Lord's tender mercies. I was surprised at the topic given the tragic event. They shared stories of special moments with their young daughter during her life and even the few hours before the accident that they were grateful for that they felt came directly from the Lord.
You sound like an amazing father and I can't imagine your pain. I keep refreshing hoping your post does not exist. I pray for you and your family and hope eventually thoughts of some moments with your son--special times that could only be facilitated by Him--will somehow ease a small portion of this anguish.
God speed, brother.