I agree with Morph, a second body is a must for anyone offering a photography service whether its portraiture, weddings and/or events.
When shooting a wedding or location shoot/event, I carry two A77's and have the the following with me;
8mm Fisheye, 16-50mm, 70-200mm, 50mm, 90mm Macro. 8 batteries, 6-8 spare memory cards, 2 x 43AM flash's, Cleaning Equipment and bottle of water. I sometimes carry my Macbook but not always.
Bag 2. (normally in car or accessable place)
Tripod, 2 x 42AM Flash, 2 x YN560II Flash, Pixel Opas Triggers, 4 Light Stands, Various diffusers/modifiers.
It may seem like allot of kit to be carrying around, but I'd rather have too much than too little.