What is the tone in Nadine Gordimer's "Once upon a Time"?

Two separate tones are evident in Nadine Gordimer's short story: one for the frame story and one for the bedtime story. In the frame story, readers can discern a tone of nervous resignation that comes from assuming corporate guilt despite one's personal innocence. Presumably, the narrator does not subscribe to the racial prejudice and exploitation of people of color that characterizes her society. Although she is white and privileged, she doesn't relish her status, knowing it has been built on the foundation of apartheid, a system that is at that moment undermining the stability of her culture just as the goldmine is causing her home to shift and buckle. She fears civic unrest, but she hasn't barred her windows or purchased a handgun to protect herself. Some "voice in the echo-chamber of the subconscious" tells her that if she becomes a victim of the exploited classes, it will not be completely without cause. 
The tone of the bedtime story, on the other hand, is ironic. As the narrator relates the tale of the family who desires to protect its wealth and status from "people of another color," readers know the narrator does not approve of their actions. Readers realize the family is harming themselves through their fear and prejudice; they end up living in a prison of their own making; it is even called a "concentration camp." The family's decision to heed the advice of those who encourage further segregation and fear is obviously folly. The final irony occurs when the Dragon's Teeth structure that is meant to keep harmful people out ends up being so effective that it keeps their own son in, killing him in the process. 
The two primary tones that come through in this story are nervous resignation and tragic irony.