Don't let them be in it then. There is no reason for children to have access to the internet.
When my generation grew up the internet was much smaller and less harmfull. Almost nothing you could do would affect your AFK life.
Can you quantify this? The internet is more centralized and moderated now. “Moderator” wasn’t a job when I first got online. There’s a pretty strong argument that the internet is more safe than it used to be.
No video. Hardly any pictures. Static sites. The computer was not used for anything important like bank services or storing personal info other than some party invite letters with clipart.
You would have to get out of your way to put your self in harm's way.
Probably better to just encourage them to live a healthy, outgoing lifestyle.