changing the position of all childs of a node except the parent

I have a main node and it has 5 childs. I want to change the position.y of the 5 childs without changing the position.y of the main node.

is there a way to do this? maybe something like:

for children in mainnode.children{
children.position.y = children.position.y - 10
}

I know that this isn't right, but maybe something like it.

I have been struggling with it for days now, anybody that can help me out?