Jim,
Not sure how big your work area is. But I just use one of the propane tank type heaters. I think it's a 20,000 BTU version, but I could be way off, I'd have to double check. I work in a 3 car garage, and it heats it up rather quickly. Tank last pretty long too.
If your family members don't like you working on the car. Just tell them, the more you work on it, the faster it'll get done,
.