Your inlaws can presumably print from their phone, using MDNS to find local printers, and sending the traffic direct to the printer. They can presumably also do

Your inlaws can presumably print from their phone, using MDNS to find local printers, and sending the traffic direct to the printer. They can presumably also do airplay operating in exactly the same way. They don't need to know terms like LAN or MDNS or Bonjour or whatever.