First Vacation with the Prius

I had two firsts in the month of July, right before we went on vacation I reached the 51 mpg mark with my 2004. The second was our first vacation. We drove from Rochester NY to Virginia Beach VA, Total miles 1358 with gas milage of 35.85 mpg. Not the 40+ I was expecting, but we did have some issues.
The first is that there are 5 of us. Two adults and 3 teenagers (18 and 16 yr twins). While the kids are skinny enough to fit in the back, their weight along with my wife and I came in around 700 lbs. Add to that a roof luggage rack with 3 suitcases and the rest of the supplies in the back and I am sure we topped out at around 900lbs, way over the max weight. Also, as much as I tried to keep the car at 65 mph, there were spots where if I did not push 75 or we would have been killed. The final last three hours of the trip was from Dover Delaware to FIB and that was mostly small towns and 55 mph speed traps. So all else considered it was better than the 20 mph we get with our Caravan and I was able to do the whole trip on about 3 tanks.
Did notice one thing that has appeared on this site and that is my gas gauge was off. The trip down I would stop ~3 hours and the gauge would be on half. Each time I put in about 7-8 gals. Still have not checked to see if my 2004 had the service bulletin installed as has been recommend on this site
All in all I was very pleased. Now if I can convince the family to take this on all our trips