You need a server AV solution where the antivirus is controlled via the server. I use one at work, it is Sopos Antivirus and only the server administrator or local administrator can configure the antivirus. I also have the Sophos firewall intrgrated also, only the administrators can change/add restrictions to it. I do not know how much it costs for a small network but there are products out there that do it via the server.
Another thought is you can also do it via the mail server if you have it on your network.