I think that we open the narrative with the narrator's mother being kidnapped, killed, or having gone missing.  It is the mother's disappearance that triggers the family to leave their village and trek across Kruger Park in the first place.  While Gordimer does not bring this element back, I think that it is a safe assumption to presume that the mother is dead.  Conceivably, there is a probability of her coming back to return to the refugee camp, but, sadly, it is not very likely.  At the same time, we know that the grandmother assumes control over the family and guides them to the refugee camp.  She settles in at the camp, doing manual labor, and oversees her grandchildren's education attempts.  She becomes the force of the family and provides structure to it in a setting where disorder is present all around consciousness.