Answer :
The author includes the anecdote about the daughter's disappointment by segregation at a public amusement park to emphasize personal experiences with segregation and to illustrate the emotional impact and daily struggles faced by black children in the segregated South.
It serves to emphasize the personal connection to segregation, illustrating the immediate and intimate emotional impact that racist policies had on African-American families. Furthermore, it highlights the cruel realities of a segregated South and the daily struggles that come with it, particularly for black children.
The vivid language used describes the emotional struggle of explaining systemic injustice to a child, hence addressing the disparity of segregated parks and their impact on the innocence and psychology of youth. It ultimately reflects the broader theme of segregation's ability to inflict lasting feelings of inferiority and societal exclusion on young minds.