I was searching the internet for resources on how to begin a dialogue with our children about human trafficking, and found an article that I thought might help with your discussion. It has some pretty good thoughts on what to say, and what not to say.
Ultimately you know your child best, and you need to do what is best for them. My daughter is 9 and has a lot of anxieties, and this will be a subject to talk about in little doses, over a long period of time. If we shared everything all at once, it might completely freak her out.
You should know that our team prays frequently for you. If there is any way we can help you with this please let us know. Here is the link to the article, it is a PDF.