Unattended installs take time, a CD for each install that is currently running, and you babysitting all of the installs (formatting, etc...).
RIS or Ghost would be my bets. If you set up RIS then it will broadcast the installs to each computer, and RIS will be set up for any future use you might have. Ghost would involve you running imaging operations on 30 disks, which on one hand is nice because you can image all 30 drives before you have to do the install day. You also have each computer set up fully with whatever patches, software and security settings you like. Just make sure you run sysprep on the computer before you do the ghost image or you will have 30 computers with the same computername booting up at the same time...