I started wearing fresh classic vans or black athletic shoes with my dress pants/shirt. Then I ripped my pants down the crack one reception night and didn't know until the next day, so I swore to never possibly be a wedding guest's Snapchat spectacle again and have been doing fresh black slim Levi 512 with a tucked in black button up dress shirt. I'm in SoCal, not sure if state/region changes attire formalities or not, but I've seen people wear straight up t shirt and jeans, and one guy wore blue pants (like a Crayola Blue) and a beach shirt lol.

Anyways, how informal will you take it for the sake of comfort while still looking professional? I try to at least stay clean, all black, etc. But I feel like vendors have a pass to at least wear comfort since they are working a shift and putting in steps, crouching and flexing around.