It's two years later, and we just made this same trip again as a family--except this time, I wasn't working, and was actually able to enjoy the beach too.
We drove from our home in SW VA to Chincoteage, VA and back. The total miles were 762.9 and we used exactly 8.490 gallons, filling up at the same pump before and after--which comes out to
89.86 MPG round trip.
Our children are both a bit bigger now, and we had a little more "stuff," so our total weight was a little more than last time. The only other mechanical difference was that we have different tires now than we did last time. Everything else about the car is the same--except for two more years' worth of refinement in driving technique.
-Funkhoss