yes, how close do you plan to be to take shots? Are you planning to walk around and take closeup group shots, shoot the presentations/speeches from your seat, or what? At a typical wedding reception I would use my 24-105 for wandering around cocktail hour and (since I can get close) for speeches/dances. I've also used the 70-200 for speeches/dance and shooting reactions in larger venues. Since you will likely not be that close the 70-200/2.8IS would be invaluable, IMHO.
I would take 24-105, 70-200, and the flash; that should cover you pretty well. I would expect the lighting to be good enough to be able to shoot without flash
Current: 5DM3, 6D, 8mm fish, 24-105/4IS, 35/2IS, 70-200/2.8IS, 85/1.8, 100-400/IS v1, lensbaby composer with edge 80, 580's and AB800's
Formerly: 80D, 7D, 300D, 5D, 5DM2, 20D, 50D, 1DM2, 17-55IS, 24-70/2.8, 28-135IS, 40/2.8, 50/1.8, 50/1.4, 70-200/4IS, 70-300IS, 70-200/2.8, 100 macro, 400/5.6, tammy 17-50 and 28-75, sigma 50 macro & 100-300