How do I make the internet safe for my children?

Tell your children that they might end up on harmful pages with anything but childish content. You must explain to your children that if something alarmed them, they can always turn to you

You can install mac keylogger https://www.refog.com/mac-keylogger.html
This is a program that can be easily installed on a computer and will work invisibly for your children. 

With Refog Keylogger Mac, all keystrokes are recorded on the computer. Each time a key is pressed by a user the program records that keystroke. Screenshots of computer usage are also taken periodically and saved for your viewing. Additionally, outgoing chat messages, Web site visits, and application uses can all be recorded by the software. 

I also think that the safety of our children is very important in the modern world. By the way, I recently found an article Scam At the Ritz Casino https://www.casinozca.com/content/scam-at-the-ritz-casino-627.html on my son's phone and now I don’t know I need to worry about this?