As Jon pointed out D7500 is among the RAW formats supported by Apple’s core engine, which means Photos and many (most?) of the photo editors listed on the App Store can handle your son’s images. It is not free, but Affinity Photo is arguably a strong competitor of Photoshop, is a lot less expensive, requires no subscription, uses Apple’s core engine, and is highly rated.
If we knew what it was we were doing, it wouldn't be called research, would it?
