What does Mama want to do to stop the Wallaces from destroying young black children's lives and to protect the black families' income?

Mama wants to organize a boycott against the Wallace's store. In order to protect her children's inheritance, Big Ma signs the land over to her two sons so that it cannot be taken from them after her death, and so that it will require both of their signatures to sell it. Mr. Jamison agrees to put up the credit for a group of black families to shop in Vicksburg.