iPads do not have a conventional file system and hence have no native access to file servers. There are third-party apps such as FileBrowser that can add the ability to connect to file servers that you might look into. I would not recommend that you attempt to use iCloud on all 30 iPads. iCloud is a synchronization system designed for a single user and not really appropriate for use by a number of different users, though it could perhaps be coerced into working depending on your exact needs and workflow. Iif this is for student use I really do not recommend it. You can also look into other cloud-based sharing systems such as Dropbox.
The mini would provide more disk space. Backing up the ipads adds up after awhile. The mini or the Mac Book pro could be used as a server to. You can purchase the server software for a small fee. The mini would be less portable, but might work fine for a cart if you figure out how to secure the monitor.
There are lots of ways of moving files.
A simple and popular way to copy files and share files amoung your devices.
Configure WebDave on your server. Prefered solution if you go with a server.
This thread has good info.
Using iTunes to transfer files:
Files Connect -- The swiss army knife of remote file connect
iExplorer -- " iExplorer's disk mounting features allow you to use your iPhone, iPod or iPad like a USB flash drive."
Windows File server -- can set you mac up to server out windows shares.
"In education and business users increasingly expect to be able to access their data anytime, anywhere and from any device."
How to transfer files from your iPad to your PC with iPad to Computer Transfer
More ways to transfer files and access Word documents:
Try the combo of:
Diskaid on your computer and FileAppPro on your iPad
Good old FTP
FileApp and FileApp Pro
I use Mac OS pureFTP server. It comes as part of PureFTPd Manager software download at this site.