[rewriting your question without assumptions about the solution]
Q: "How do I find what OS/Device is connected to our wifi?"
Don't use mac-addresses to determine endpoint operating systems; mac-addresses are easily spoofed, and vendors can change their wifi PHY ASIC supplier on a whim
Use something like DHCP FingerprintingDHCP Fingerprinting, or better still, Cisco ISE (which does DHCP, HTTP, RADIUS EAP supplicant, and
nmap
fingerprinting, all in one appliance)