Jack, I suggest a lil changes on the who should bring what....

The list of things can be as below

1. Which can be totally handed to each one person OR best purchased by a group and share the cost:
a. Drinks
b. Water
c. chips/chocolates & bread
d. Disposable Plates, spoons, glasses & napkins
e. Burgers & Sausages
f. BBQ items
g. Charcoal
h. Garbage Bags
i. thongs (:P)

2. Stuff everyone can bring their own
a. Chairs
b. Tent (if anyone can arrange)
c. Sound & Light (if anyone can arrange)

This is a suggestion & I usually do that when u go out on BBQ parties...:)