here's a few options: If your car hasn't been effected and you have some gas you can buy a small power inverter from radio shack and hook up the heater to the cars cigarette lighter. Add a battery powered airstone to put some oxygen into the water. If you dont have them stir the water up with a wooden spoon.
2. like someone else mentioned use water bottles filled with hot water, then float them in the tank. Also can add warm water during water changes. The hand warmers might work, just put them into a container or something so the chemicals can't get into the water.
3. Maybe temporarily re-home them until the power comes back on.
I know how ya feel, I just went through the same thing, luckily all of my fish made it through the storm. Lots of devastation on LI, and staten island, glad u guys made it through ok