Michigan here. I’ll use worse case scenario and say it happens in dead of winter.
power outage- their soon to be in their own insulated small room. So plan there is generator + space heater. My generator is big enough to run their heating equipment plus the space heater and my sump pump, lights, and some to spare. Eventually plan on getting it connected to my house to where I can power my furnace and such with it easily. It’s a 7000watt generator.
carbon monoxide- I have a couple large tubs. Pack them on there. Straight out to running vehicle with the heat on...then off to
the hotel or friends or where ever we stay. The tubs I use can be locked and securely shut.