Well...I'm not going to say that I'm a computer networking expert. But when I was in college, working in one of the computer labs (Macintosh's)...you needed one computer to act as the "server"...and then you needed one computer for each user.
The server "shared" the software...which would require a multi-user license for each application shared. Plus you needed the special "server" software, and certain Apple computer models were specially designed as "server" models.
So if most or all of these parameters still hold true...for a server setup you would need:
- one more computer than you have users (in this case 3 kid computers + 1 adult computer + server computer = 5 computers)
- server software
- multi-license application software (including the Mac OS)
So I would think that a "Server" setup would be more expensive than buying 4 separate iMac's or Mac-Mini's.
If you already have compatible monitors, keyboards, and mice...then the lowest cost route would be to purchase 4 Mac-Mini's.
And an even lower cost route would be to purchase 4 used Mac-Mini's.
Hope this helps,
- Nick
p.s. BTW...you can purchase 4 Mac-Mini's for the price of one Mac Pro.