Mrs. Dalton is a wealthy blind woman who takes an interest (in a pandering, hobbyist sort of way) in the National Association for the Advancement of Colored People (NAACP) and encourages her husband to be generous with their wealth and use it to change the lives of blacks in Chicago. Mrs. Dalton’s physical blindness proves to be an apt metaphor for her social and spiritual blindness. Though she’s a religious and kindly woman, she is completely blind to the fact that much of the family’s ongoing wealth is gained through exploitation of the same black people she’s trying to help.
In addition, much of the Daltons’ generosity, as Boris Max points out, does very little to actually help anybody. (The donation of money for ping-pong tables at a Boys Club is one such example. Who even likes ping-pong?) Mrs. Dalton represents a particular type of person: a liberal, progressive white woman who fails to recognize the ways she exploits the very people she claims to help.