I ran into this issue a couple of years ago when we had a very strict internet policy. I worked with Apple and Cisco on the issue and basically found the resolution on my own.
Baically, Apple/iOS devices will need to check in with Apple when connecting to Wi-Fi.
We had apple.com blocked on our strict Wi-Fi network and the iPads would connect and when we attempt to use the Wi-Fi, it would drop out. After a week or so of troubleshooting, we saw the website block logs and there were thousands of hits being blocked.
If you have no internet at that site, I do not know how you can get it to work. Possibly if you use an internal DNS server and make all apple.com requests hit an internal site. If I recall, it was just hitting a dummy webpage with a mesage on it like "Success"