I have done two smaller weddings (100-150 people) with my PSR-3000 alone using only styles, and a couple of MIDI files for restroom breaks etc.

I will be doing a larger wedding (hundreds of attendees) shortly, using the same setup. There will be a guitarist and a percussionist accompanying me but I'd do it just the same without them. If you have your styles organized well and your song lists down, I don't see the problem.