As you will be cooking and supplying food you need to follow the food hygiene regulations. This includes ensuring that the food is kept under conditions that meet the Hazard Analysis of Critical Control Points (HACCP) - you may also have heard as this as Self-Assured Catering.
You need to do a Risk Assessment that covers food hygiene, fire precautions and any other significant hazards that your event may have. Suitable control measures will need to be documented and applied, including emergency arrangements.
The location of the BBQ will need to have the approval of the AU Campus Services Department (or Sports Centre if on their land).
If all this sounds like too much bother, you can always contact Hospitality Services and they may be able to take over the catering for you and make sure that your food is safe to eat. Alternatively, if you are a student association of the Guild, they will be able to give advice.
Food poisoning can be very dangerous. Please see these news items about E.coli infections caused by incorrect storing and cooking of food.