How do i reactivate an iPad Mini that has been disabled
How do i reactivate an iPad Mini that has been deactivated due to password without iTunes
iPad, iOS 7.1, New iPad Mini without Retina displa
You have to restore the iPad using one of the methods in here.
iOS: Forgotten passcode or device disabled after entering ...
You will need to use Find My iPhone in iCloud.com in order to erase your device and unlock it so that you can use it again. See the very end of the article.
This is copied from the article.
If you have Find My iPhone enabled, you can use Remote Wipe to erase the contents of your device. If you have been using iCloud to back up, you may be able to restore the most recent backup to reset the passcode after the device has been erased.