Wow Your Brave, I've done a similar thing but used the MSM 760 to create a number of single use 1hr accounts and then just give them out to people who need access as and when (guests, not students). We also offer Free student WiFi that authorises using a Radius server against the students username and password for the network (802.1x). Then we log all that and push their traffic through our proxy.
Hope that helps,
Tom