Another option for the girls' room could be a small electric fireplace with a blower on it. You can get a small one with glass on it so there's no way they can burn themselves and it will distribute the heat throughout the room.
They have really small ones for about $200 at Lowes or Home Depot and they're safe and efficient. They won't use much current and will do the job. Then, you can always move it to another part of the house if they go off to college or run away with a boyfriend at age 16.
The Home Depot