Honestly speaking, I've never had to shoot an event above 1600 ISO. I did a shoot a few months ago where my only light sources where Christmas lights wrapped around trees and I was so hesitant to use 1600 ISO, I forced myself to use 800 and a majority of my pics were shit. I could've bumped it up to 1600 ISO and it still would've been fine but I was scared of doing it coz this was the last day for the Christmas lights and there wouldn't be any reshoots.
But on the other hand, that's when I learned how great Lightroom's noise suppression is. Once I narrowed down a few shots that I really liked, I spent my time playing around with noise removal and all that good stuff... and the pictures turned out really well.
Worse comes to worse, you can play off the grainy-ness as an artistic quality that you were trying to achieve lol.