Need some advice for small office - eviltoast

I’m looking to set up network monitoring on my small 4 person office. The things I’m most concerned with are websites visited, bandwidth usage, and internet searches. I’ve already mentioned to the group that even though they bring their own laptops to the office, while they’re “on the clock” we can’t have people visiting gambling, porn or any website that could be considered offensive …thus making me liable for some kind of lawsuit.

So ideally it would be:

  • Agentless (I’d prefer to not install anything on their personal laptops)
  • Router/Firewall Based
  • Not too expensive :)