I know that PARAT solutions offer a great piece of hardware for syncing up to 20 iPods. http://www.paratsolutions.com/products.html . Maybe they do something for iPad?
Also for some advice on syncing multiple devices this is a good blog (also offers great free resources for teachers):
I think this is what you are looking for.
Here's another link that may help: http://wiki.canby.k12.or.us/groups/ipodusergroup/wiki/adfd8/Buildin...