Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
You can set your server to block certain specified sites, definitely.
But setting the WiFi access to block sites is somewhat less likely. Some routers have, if my memory served, had built into their configuration a Parental Control facility that could block certain websites.
Would that do for your needs, and for this purpose?
I have not heard of that sort of router at all. I suspect there is no such router... but I am looking it up:
... what you are looking for, is not a router box of any kind, but rather a RADIUS authentication server. That can provide each login to the wireless with their own password.
Have a good evening, please. Let me know when you are ready to resume. Thanks.