OS X only trusts certain devices for GPS info (ones in the 'made for iOS' - MFi programme). You can try setting up your phone to send it to iOS but I doubt it would work. Getting GPS out of iOS is simpler than getting it back in to be used as the system wide location services feature, so be careful to read any sources that discuss 'share gps with iOS', they may be going in the opposite direction.
It is probably simpler to purchase a GPS enabled add on. Bad Elf make ones that are compatible with iOS, take a look & then use Amazon to compare to other makers.
http://bad-elf.com/collections/plug-in-gps (look for Bluetooth based ones too).
I would also suggest you install the Pokemon Go app now if you do not already have it. It may be that it the app store prevents it being installed because your iPad does not have built in GPS. The game requires it for obvious reasons. I think it may also require a gyroscope for the augmented reality part, I don't know if your iPad has that?
I doubt wifi & Bluetooth are accurate enough, you need to be in about 20 - 30 feet for Pokestops often in parks etc, which wifi & Bluetooth cannot support very well at all.
It's kinda difficult to get a game anyway - you also need a constant cellular connection - so your iPad will also need that too. Frankly you may want to look at getting the cheapest second hand iOS device that supports iOS 8, GPS and cellular if you really want Pokemon Go.
