Well, something needs to change on a per object basis, so that part needs to be in the ‘descendant’. I think that’s your problem at the moment, you’re trying to put item specific stuff in the parent.
You either need to do something in every child so you can always use the same pivot point in the parent. A scene component would do the trick. You can have it in the parent, but move it to the correct place in the child.
I just tried it, it works. So you just have a scene component in the parent, which you can position in the child. All the parent has to do is put the scene component on the ground / surface.