I’m doing something similar with my doorbell. I don’t have easy access to wires coming from the button, so I set up a relay to switch the power being outfitted from the transformer.
I’m using an Arduino Mega with an Ethernet shield and MQTT rather than the GPIO pins. I have time based rules that shut off the doorbell for my son’s nap time and for bedtime. I also have the switch exposed to HomeKit so I can shut it off manually when I work nights (notice how two night shift workers thought of this 
).
At some point I’ll venture into my attic to pursue a more robust solution like yours but for now this helps us stay asleep when the delivery guy comes.
As the pictures show, I’m doing a lot more with the arduino than control the doorbell so my code might not be too helpful… but if there’s interest I will post snippets.
