Hoppy please accept my condolences also on the death of your dd's classmates.
There would be plenty of things to help conceal a grave in the woods that would make it very hard to detect or even see the ground had been disturbed.
Just wondering if AB was tasked with keeping an eye on the 6yo and EO was over there often playing therefore having to watch them both. AB dug 2 graves, one for each girl, so she would no longer be responsible for watching them.
I am still convinced AB also had RAD. As I have said before a RAD child is very sneaky, coniving, and also sweet and innocent.