You could use the Iphone Wifi Presence sensor https://community.hubitat.com/t/updated-iphone-wifi-presence-sensor and create a virtual presence for visitor. When his stay is over, then you just disable the Wifi Presence and leave it available for any other future visitors you may have. I do this when I have family coming into town for extended stays.
Make sure when the visitor connects to your wifi initially, that you have them turn off MAC randomization.