Aisha's Moonlit Walk by Anika Stafford (Skinner House Books, 2005) has a story about a young girl who moves past her shyness to stand up and speak at a public gathering.
Read The Agitator's Daughter by Sheryll Cashin, or watch a CNN cablecast of her 2008 talk at the Politics & Prose Bookstore in Washington, DC. John Cashin, her father, is present in the audience.
Reach & Teach carries many products useful in teaching children about justice.
Parents as Social Justice Educators, by Roberta and Christopher Nelson, is a useful curriculum for parent groups. It can be purchased as part of The Parent Trilogy from inSpirit: The UU Book and Gift Shop.