Good evening. I feel certain I can assemble the desired software; changing the Wifi password on the network should be as simple as connecting to the router's control panel, usually via HTML. Reconnecting any computers you wish to use with this network connection will also be easy; instigating a temporary freeze on the cycle to allow a new computer to connect should also be easy.
In order to start work, I will need the router control panel pages (usually HTML files; download can be difficult but I can help with that as well) and a list of the operating systems of the computers you wish to keep regularly connected to the network. (Note there will be a period of probably a couple seconds of disconnect each time the password is changed; datastreams may be interrupted.)