Equipment used to shoot:
For 90% of the Shoots (esp for wedding dinner)
1DmkII +24-70L
580EX + Lightsphere + External Power Pack (CP-E3)
For the last 10%,
I would use either a 85L or 70-200/2.8L IS
If I was using my old equipment, it would just be my 300D + 18-125 Sigma. I would still use the 580EX+Diffuser+CP-E3. Personally, I think the flash, diffuser, powerpack combo is almost a must for wedding photography esp for the wedding dinner. In the day, you might have enough light, but in the evening, you need as much light as you need. While using a fast lens might help in focusing, the low DOF will work against you, and I regularly use f5.6 even on my 24-70L. So with f5.6 and ISO 3200, you might still end up with impractical shutter speed. I rather set my ISO to between 800 to 1600, shutter at 1/125, f5.6 and let the flash do the work. The lightsphere diffuser will work very well to provide a combination of bounce flash(if ceiling is low) and indirect flash. I also cannot help but recommend use a wide angle lens as since you are using indirect flash with f5.6, your flash range is only a few metres. Using a wide angle helps you stay closer to your subject so your flash can cover it. Also in wedding dinner, it is very tight and hard to back up.
Personally, if you are going to shoot event or wedding, it is a MUST to learn how to use flash. Why? Because you simply have no time to figure out if your photo has hand shake, subject shake, under exposure or wrong focusing. Half the time you are watching the scene trying to catch the moment. There is no second try, you must get it the first time. If you set your camera and workflow correctly, flash photography makes things so much more safe. You just have to make sure your subject is not too far away such that the flash cannot reach it and you focus correctly. ETTL will handle the rest and you will assured with a perfectly exposed picture with no hand or subject shake. Some may say that the flash might kill the mood of the pictures, but if you weigh in all the uncertainties and troubles of using a fast prime and slow shutter speed, I rather go for my flash. I am saying this as a primary photography at weddings and event. If i am a guest at the wedding or a secondary photography, I will whip out the primes and shoot because I am not shooting the "money" shots. I am allowed to miss critical shots as the primary photog will get it anyway. I can either shoot a more arty kind of photos or push the camera to shoot without flash.
Anyway that is the way i work. I tried shooting events with primes, fast zooms, slow zoom, ultra zoom and I find that in the end, a wide normal zoom with a battery powered diffused flash is the best compromise. I dont have to think about technicalities of the photography and can focus on capturing the moment. Most weddings and events happens only once. You cannot expect the bride to go back and walk down the aisle again because you screwed up.