i did help out my friend for his wedding... (not hired... just that his photographers refused to go his place stating miss-communication of locations and other stories... and asking him to top up for about a grand to get his wedding day photoed...)
i find that external flash (which i don't have it until today) is quite the most important thing... no flash can't do candid, no flash can't do proper portrait, no flash can't get the best possible group portrait...
the reason: indoor even using f/2.8 all the time, i experienced sometimes aperture priority hit 1/30s shutter even on ISO 800... the shutter speed looks "okay" to me on the spot since i know i won't get shaky photos with ultra wide at the lowest 1/30s shutter speed... went home review found that it's not the shaky hands that matter... the rather slow shutter speed won't get you nice photos when people moved, or kids running around, and some moments (mostly the couple's emotion) that last less than a second...
if i were to do it again... i would buy a proper external flash (or at least rent one)...