Cal,
Your trailer & car will be one of many at the track. The track is usually very secure, and they have thier own staff to patrol and man the gates. It's very rare there is ever a problem at this or any large marque gathering, as we are all looking out for each other. I have left mine at many, never an issue.
Best advice? The track is good and safe, relax, enjoy the weekend. It's your first, you will overload on all things Shelby, Mustang, Racing. Have a cold beverage and enjoy!