I looked at this event yesterday. Good Guys website states that they do NOT provide security for cars left on the grounds. Their will be plenty of people traveling to this event and have no other choice but to leave their cars. The vendor at the booth you will be setup may have someone sticking around after hours (if allowed) to keep a watchful eye on their products and your car. It will probably be okay sitting out there for a few days due to the size of the event and it is a class act function. It is on the infield of the track and not just anyone can get into that place after hours, plus I am sure yours is not the only car left out.
I would still be on the fence leaving mine out there, without me personally keeping an eye on it. Not sure how your insurance would look at that too if in the event something happened and you live within only 15 mins. from the track. This 1st event being held in March is questionable too, it will be spring time in Texas = possible storms. Just something to think about...
The last time I went as a spectator the cars were parked so close together I felt uncomfortable just walking around them. I drive the dog snot out of my '55 that is very nice and it is no trailer queen but man, people today just don't care or watch their kids close enough at these car shows. Been to many shows and have seen others push there way in with baby strollers and little ones just touching away- YIKES !
BTW... The guys at CNC are top notch !
Best of Luck