Help me find adult woman lady clothes in under three hours?

I'm a part of my democratic town committee and will be attending a fundraiser/meet-n-greet tonight in town for a Congressperson. I also donated all the wine for the event, and will be helping to serve/pour because of course I am.

The event is outdoors at a local Dem leader's house. She's a lovely, laid back, retired Liberal, who is sort of the "seat of her pants" type. The weather is supposed to be lovely and about 75 degrees this evening. I will be standing on a cement patio most of the time, so I was eyeballing my Chucks, but I feel that would be pushing it.

What do I put on my body for this event? Why do I feel this is harder to dress for than a regular business thing? SHOULD I WEAR PEARLS?! I feel like pearls should be a thing.