Yes, all iOS devices equipped with a Touch ID fingerprint sensor like the iPad mini 3 and iPad Air 2 support Apple Pay, however, this does not mean they support in-store payments. Only iOS devices with a NFC chip can be used to make in-store payments at Apple Pay terminals. The only Apple two devices with NFC are the iPhone 6 and iPhone 6 Plus.
iPad mini 3 and iPad Air 3 users can only use Apple Pay to make online and in-app purchases on their tablets.
The Apple Watch can also make in-store payments when paired with an iPhone 5 or later.