Here is I think, a win-win piece of advice. Drive now while you can. Take care of your parents. If the storm misses, you've visited family that may not be here forever, and if it does hit you will be able to evacuate them in time. Waiting may prevent both of those options. Ask yourself; "Can they do it withou my help?" Unless the answer is a resounding YES, Put a 5 gallon jerry can of gas in the car, refuel every 1/3 tank (in case stations in the destination are out of gas or lines robbing valuable time, and drive there like a life might depend on it.