Thats a typical cause. Itunes sees that there's content on the device associated with another account and wants you to sign into that account on computer. It might be best to set up all devices as new, then sync with itunes, all with same computer, same itunes library, same account name.
Since you're trying to set up several deivices in an enterprise environment, you may want to look into this:
Enterprise/Business/Education
Apple Configurator (multiple device configuration)
https://itunes.apple.com/us/app/apple-configurator/id434433123?mt=12
Mobile Device Management
Amtelnet MDM
http://www.amtelnet.com/mdm/mobile-device-management.php
Meraki MDM
http://www.meraki.com/products/systems-manager/
Here's information regarding rolling out iOS devices across an organisation, business or educational establishment:
http://www.apple.com/support/ipad/enterprise/
And here's about bulk app purchasing:
http://www.apple.com/business/vpp/