Boo reflects innocence as he places childlike toys in the tree to extend a hand of friendship to Jem and Scout. He also exudes innocence at the end of the novel when he goes into Jem's room and wants to touch him to make sure that he is okay. Both of these acts show a man who is innocent of any hatred, malice, or other vices that adults often get darkened by in life. He is innocenlty desiring to create a bond with these children that is as special as a bond of friendship and as strong as a familial tie.
Jem exhibits innocence when he cries after the Tom Robinson verdict comes back guilty. He is shocked that people could make such an evil choice, when Tom was so obviously innocent. His shock at that, and his tears, show his innocence to the world's more unfortunate realities. Jem also shows innocence when the thought of getting in trouble with Atticus (when he lost his pants in the Radley yard) is so upsetting to him. He still lives in a world where he cares what his father thinks of him, and want to preserve their good relationship. That shows his innocent nature.
Scout shows her innocence when she talks to Walter Cunningham, who is part of the angry mob outside of the jail. She doesn't really understand just how dangerous the situation is, and thinks it is strange that all these men, who she knows, would be acting that way. So, in her innocence, she talks to Walter and that is the act that helps Walter to realize just how ridiculous it was. He walks away and take the mob with him. Scout's innocent nature saved the day. She also shows innocence in all of her many questions. She is innocent to the fact that maybe some questions aren't right for certain situations, and she often creates uncomfortable moments as a result. Consider when she asks Aunt Alexandra where her husband is, when she asks Cal why she talks funny at the church, when she asks Cal what rape is, when she asks Cal why people are taking up a collection for Tom's family...all of these questions show her childlike innocence, her curiosity, and the fact that she has some learning to do about social situations.
I hope those examples help; it's an interesting question. Good luck!