You could say that when Scout says, "Autumn and Boo's children needed him" is an example of verbal irony. Technically, verbal irony is used when a character knowingly says one thing but means another. Situational irony would be if the character says one thing and unknowingly means another. In this case of situational irony, the audience, or reader, usually knows the character's mistake. But with verbal irony, the character or narrator knows the irony of what he/she is saying. When Scout refers to herself, Jem and Dill as Boo's children, she does so with the knowledge that they previously viewed him as a recluse, even as a monster. It is ironic that, in her eyes, he was once a monster and now, at the novel's end, she sees him more like a guardian angel.
There is also a subtle intertextual reference at the end of the chapter that is an example of verbal irony. Scout asks Atticus to read aloud The Gray Ghost. In this book, there is a character like Boo who is blamed for something that he did not do. Atticus protests but then relents when Scout tells him she isn't scared. In fact, she says, "Besides, nothin's real scary except in books." In Scout's recounting, the character in The Gray Ghost, Stoner's Boy, was accused of some things and was then found to be innocent or "real nice" as Scout put it. The same was true of Boo Radley. This may be more situational irony because Scout is half asleep when she says this and probably doesn't consciously make the connection to Boo. However, since To Kill a Mockingbird is narrated by Scout as an adult looking back on her childhood, I think this is an example of verbal irony because the narrator knowingly included this comparison of Boo and his textual alter-ego in The Gray Ghost.
Scout is no longer scared of Boo. This is because he saved them from Mr. Ewell but it is also indicative of Scout's maturity. It is ironic that she says there's nothing scary except in books because it was essentially gossip in the form of stories (not actual experiences) of Boo which scared her in the first place. She and the other kids were scared by the stories they'd heard about Boo. But once she met him, he turned out to be "real nice," and a kind of guardian.