I did a 3hr shoot they got married last week in CHCH and now here just some speeches without the I do stuff, 1hr service and 2hr lunch next door at the church's kitchen at a suburban church. 

How do you guys do candid when people are on red alert when you silently get behind them and they won't let their guard down. 

Also in our instance, the service is all inside then they wanted the group shots taken inside the church before they head out to the lunch next door, 2min setup at the front stage inside the church bam bam bam like 9 sets of photograph and then everyone bundled into the building next door for a light lunch 2hr of that and then it was home time.  So with even a 2.8 the background was messy, kids stuck into their circles like american football timeouts  there were also no tables during lunch it was just a large long table down the room self serving and chairs on the side of the room. 

Very informal I know.  If it was you pro's what would you have done?  For the group shots I switched from 2 shoothru brollies to 1 reflective brolly but in hindsight I think I shoulda just went for a single hotshoe flash.  Also the church's ceiling is like 4 levels high and it was all brown timber same goes with the extreme left and white walls.  They already had a pro who did the photo's beside the lake at Tekapo and/or Wanaka and they had the first marriage ceremony last Saturday last week.