I like this one from the very end of the book, when Ralph has finally been rescued.
And in the middle of them, with filthy body, matted hair, and unwiped nose, Ralph wept for the end of innocence, the darkness of man’s heart, and the fall through the air of the true, wise friend called Piggy.
The "them" in the quote is Ralph's rescuers. The quote is quite clear in its intent. It's so clear in fact, that I believe it isn't Ralph thinking it. I believe it is Golding speaking directly to the reader. In either case, the quote reaffirms to the reader that the boys started life on the island as innocent children, and that they all have lost that innocence through their horrific experience. Ralph has witnessed true evil blossoming from boys that he once called his friends. He has witnessed violence, destruction, murder, betrayal, and sacrifice. He truly has lost all of the innocence that he once had.
You could use this quote too.
Yes, laugh. Go on, laugh. There’s them on this island as would laugh at anything. And what happened? What’s grown-ups goin’ to think? Young Simon was murdered.
Piggy is saying this quote. It shows innocence and experience, because Piggy is explaining the loss of innocence through the murder of Simon. Simon also happens to be the most innocent of all the characters in the book as well.