Installing German language iOS on iPad Air

I have an iPad Air that currently has the American version of iOS 8.3 installed. We would like to give this iPad to my father-in-law, who is German and is currently visiting us in the US. He is not terribly tech-savvy, so I would like to install the German version of iOS for him while he's here and let him get used to it before he returns to Germany next month.

I assume that this will involve restoring the iPad, but how do I get it to download and install the German version of iOS while it's still in the US?

Thanks in advance for any help.

Mark