Have a little treasure map along with you so you are certain you get enough charge at each stop.
Treasure map - I mean how many miles between each charging stop (maybe even alternatives). From your last stop before the race, you'll probably want to count round trip to the next charge station. More than likely a 100% charge.
Give yourself a cushion to reach each stop. If you have to get 100%, if the charging slows down near the end, count that time in.
Getting home might be easier than you think. If you need two or three hours of charging - go to sleep. Remember the car is awesome to sleep in since you can leave the AC and music on while plugged in.
This might end up being the most relaxing trip you've ever made.
Double check your math. I've done a couple of stupid mistakes with charge times. The most recent, I only had 20 miles range left when I got to the hotel, and I had no idea where I was getting my charge the next morning (turned out the hotel let me use a 110V outlet overnight).
Have a great time.
If you figure out how to make the trip easily - July 20 is Refuel - an all electric car event at the track.
http://www.refuelraces.com/