What did Donald do on “Take Your Child to Work Day”? How does Donald prepare for this? What does Donald learn about his father’s work?

Donald had to go to school because his father wasn't allowed to take him on his mail route. Instead, his father plans out a special mail route for Sunday. On Sunday, Mr. Zinkoff gives his son a mail carrier hat and says he will be paid five dollars at the end of the day. Donald delivers letters he has written and put into envelopes with postage stamps drawn in crayon.

In Chapter 12, "The Nine Hundred Block of Willow," begins at lunchtime, during which father and son discuss weather. Donald admires his father's ability to deliver mail under all weather conditions. After lunch, he begins delivering letters again and sees the Waiting Man. Mr. Zinkoff says the Waiting Man always stands behind the window waiting for his brother, who has been missing in action from Vietnam for thirty-two years. Donald meets a lady with a walker who thanks him for the letter.
Donald is so sad when the day's work is finished that he cries all the way home.