We have a 7-year old daughter with friends that have these speakers, so she knows how they work. My concern is that she will just press the button on the speaker to turn the functionality back on if that is the only way to turn it off.
Best answer by Chris
To get Sonos ONe to have voice control you have to not only have the microphone on as you say. You also have to sign up and set it up in the Alexa app. If you don't setup in alexa app the microphone on/off doesn't matter - it has no alexa.
You can set it up in the Alexa app - but if you want to temporarily disable go into the Alexa app and mark it as disabled. That would be a way to turn off when you want but not be as simple as turning the microphone on/off.