Newbie question here...I need to create a closed mac network.
Please forgive the nitpicking, there is great information listed above about how to best accomplish your goals.
You can ALSO setup one of the mac minis or any computer actually as a wireless server. On a mac it is as simple as clicking the WiFi icon > Create Network. Give it a funny name, something like WindowsAntiVirus and have the rest of the computer connect to this computer via their WiFi. The WindowsAntiVirus computer should have a web server (MAMP) running for them to pop into by default. A simple WordPress site with links and daily assignments is what we have in our test lab. This isolates the lab from the 'real' internet and allows the lab to see only what you've previously downloaded and made accessible. It also focuses them on the daily tasks. Easy to do and up to 255 clients can connect simultaneously.
iPads, windows computers, androids, Macs, whatever can 'log in'.
PS. The server does so much more. We create tests that the students take 'online' with their iPads / Macs / PCs / Chromebooks. This gives us immediate results, we can watch the test being taken and see struggling students in real time. We take and keep attendance records with it. We can serve videos, documents, ect. Saving the best to last. When the power goes out, everything stops, except in the lab. The server is running off of battery backup. The iPads, laptops, chromebooks are still connected, and testing, studying, whatever.. in the dim glow of the computer screens and emergency lighting. It doesn't matter that the main WiFi has gone off line. Grades and attendance and homework is still getting turned in.
PPS. The mac vulnerabilities comment was hilarious. I work in the same environment. We have a company that makes money off stuff breaking ( Windows ) and licenses ( Office365, Windows8.1 Pro, ect, ) and repairs. Most of this would go away if we ran all Ubuntu or Macs on an Ubuntu server. They would lose their millions of dollars contract. 100s of people would lose their jobs. So it is in their best interest to dissuade users from Macs. Ignorance of other Operating Systems kills me. It is like computer racism. Did I just type that?
Oh my.