I don't know that I necessarily agree that a child's death affects fewer people because the deceased is a child. If that child attends school, EVERYONE in that school is affected. I just left the wake of a 15 yr old. She was in high school, one of the largest high schools
in the city. She was involved. She has siblings. Her classmates, her teachers, her siblings' classmates and teachers are all directly impacted by her death. The empty chair that belonged to her will be there and her absence will be felt. I remember the empty chair of a classmate when I was in high school. The deaths of the children I've worked with in all my years as a pedi nurse have, without a doubt, impacted me more than the deaths of the adults in my life, relatives included.
I do agree that the grief process is completely different. As a parent, you never expect that you will bury your child. As a son or daughter, you realize from a very young age that you will likely outlive your parents. You might not expect cancer or to lose them at a young-ish age but you do understand that at some point in your life you will have to say good-bye to your parents.