Hmmm, I can see the story, but there are a couple of issues. A “Young Boy” in my mind implies someone around the age of 10 or younger, so I wonder how he would be able to help free and stop a slave trade, plus I don’t think he needs to reevaluate his ethics, as you mentioned he’s trusting, so I assume he is ethical it is more he should come to realise the world isn’t how he perceives, which works as boy loses his innocence, plus this reevaluation is more of the arc of the story, so probably don’t need it in the logline.?

I, personally, would turn it on his head, what if it was his family that were traders, what if the people he always thought as staying were actually people being sold. Then he’s challenged by one girl, who he gets to know, who tells him she isn’t who his family is saying she is, but they are the bad ones, now he has a real choice between family, who do appear to show him love and affection and doing what’s right.

You still have stakes, as this person could rescue the girl before she is sold, and if he can get her to safety she could reveal his parents dark secret, maybe at first she claims she’ll just leave, but when she helps him, she states she is going to hand his parents in to the police, now he’s faced again with that choice.

I hope that helps.