driver of cars, this should NOT be a problem. plenty of reasonable ideas already, I'll give you what has worked FOR ME.
ensure that you plan for the drive to actually be EIGHT hours. drive 90min, pull off at a random side road/rest stop/dirt road (this is best). get out and jog 3-5min (less than a mile). drive another 90min, repeat. continue until you get to your destination.
viola, no "stiff-leggedness", no soreness, you feel perky the entire drive (sorry, poor choice of words there ;), and you get just enough mileage for the day to "shake" your legs out. please post back on this thread and let us know what you did, how you felt when you arrived, and how the race went. best of luck, grab a PR!