In the children it is an abstract idea. The distance the camera opens with, to me, implies the distance the children feel to the concept of death or the concept of the creature stalking them. They play games and they entertain the idea to scare each other, but its all in the playful manner of children.
As the scene progresses, we follow the adults, and the camera grows tighter and more claustrophobic, tightening in on that very real fear in the mother as she performs her tasks, casting long shadows in turn.
This culminates at the end of the clip with the child playfully interact