Without using a schedule, your router would have to support upnp to accept the commands to authorize / de-authorize a mac address. And you would probably have to write the handler for it 
There is a netgear nighthawk device type that may work… Haven’t looked at it real good but perhaps it can cut the wifi - you could keep your cameras on the “guest” access then cut that off when the presence sensors detect presence.
https://community.smartthings.com/t/release-netgear-nighthawk-router/110986
Alternately you could run all your cameras through a separate router or wifi extender on a different SSID, but on the same network / subnet. Then use the presence sensor to cut power to the router / extender.