I wear a fanny pack and carry a backpack. The fanny pack (a small size one) is just big enough to carry my room key, car keys, 1 credit card (just in case something happens to my room key), drivers license, a little money, klenex, wet ones, and glasses. The back pack has DH and my ponchos, jackets, camcorder, exta batteries and memory, and umbrella. I wouldn't give up my back pack for anything!
In choosing a backpack look for 3 things.
1. Light color, that way it won't absorb the heat.
2. Make sure it is comfortable to wear!
3. Make sure it is not rigid, the material is moveable.
Have fun!