What a great event the Petite is. I went every year that I lived in Atlanta but unfortunately haven't made it back recently since moving away. There are so many great viewing spots. Definitely make it a point to walk the inside of the track ... it will take time but it's a long race
If they aren't sold out you'll want to spend extra for an infield parking pass. If you don't have one you have to park outside the track across and down the street in a field quite aways from the entrance. Plenty of food, drink and merchandise once inside.
Couple of suggestions ... if you have a small folding chair bring it and carry it around with you as there aren't very many grandstands / permanent seating ... bring plenty of batteries for your camera as outlets are hard to find when you need to plug in a charger ... wear your most comfortable walking shoes ... consider camping - additional cost from the ticket but lots of fun.
Enjoy and post plenty of pics !