I'll do little ones, because I have a six-year-old.
First, you don't begin this discussion once they're a tween. As soon as they're picking up technology—a three-year-old picks up an iPad—you're beginning to enter into that discussion and that dialogue. I think it's really important that children are accustomed to hearing from you about what they're doing online. It isn't a foreign thing for you to be invested and interested in what they're doing.
I think where some of the defensiveness comes is that all of a sudden parents enter into it. They're terrified, they're aggressive, and kids tell them to back off; it's none of their business. Then they're a teenager and they want to tell you nothing about what's going on. I'm not saying you won't get pushback, but it won't be strange for them to hear you talk about those concerns.
As we mentioned, our material walks through the different ages, recognizing that you can be very rule-based with an eight-year-old; good luck on trying that with a 13-year-old. It doesn't work. You have to evolve your messaging as your children age. If you miss that piece, you will have some problems.
You also can't bury your head in the sand. This is not an issue that happens to marginalized children; it happens to every child, whether they're exploited by someone online, whether they're being sexually abused. This is not a problem that happens to a certain segment of our population or somewhere else in the world.