Remove iPad Mini 4 from Find My iPhone without Wi-Fi
You can remove the iPad from your account by visiting iCloud website using a web browser. Follow the below mentioned steps:


Visit iCloud website on your computer and login with your Apple ID.
Click on Find My iPhone.
Select your iPad.
Click on Remove from Account and follow any further steps.






Update: As of this writing, the aforementioned steps to remove a linked Apple device by visiting iCloud website has been revamped. To remove a linked device, follow these steps:


Visit iCloud website on your computer and login with your Apple ID.
Click on Settings.
Under My Devices section, click on your device (iPad in your case).
An overlay view will open, listing all your linked devices. Click on the blue circle with a cross to remove your device and confirm your intent.


Here's what the new UI looks like: