If the screen will not respond, there is no way to turn off Find My iPad/iPhone. It cannot be turned off remotely.
I don't think that this is correct. I was able to remove a troublesome iPad from this setting remotely using iCloud.com.
1. Log in to iCloud.com
2. Go to Find My iPhone
3. Look for all devices
4. Click remove device (or X icon) next to the device in question
I did these actions to remove an iPad and do a factory reset in order to correct an Apple ID issue we were having with my son's iPad. The steps to reset it worked best by clicking "Erase" and basically remote wiping and reinstalling from a recent backup.