I would say get a block heater if you can plug it in at home. It take some fore-thought, but definitely better than letting the car sit.
You can also get a seat heater.
Heated Seat Cushion Bring it inside for the night, so it doesn't get cold outside overnight, then plug it in, put the kiddo in and they'll be toasty warm along with the pre-heated engine pumping out heat through the vents.