Hair for Wedding (as a guest)?

My aunt is getting married and I have no idea what to do with my hair. Its an evening wedding, but its not super formal. My dress has thin straps and a square neckline. I have medium long hair with layers. I also have bangs that I normally straighten and wear to the side (I can't go without them). My hair is naturally wavy, but most of the time it poofs and frizzes. The hair style has to be somewhat durable, because I have to get ready in the late afternoon, then walk across a windy campus, take an exam, run back, sit in the car for 3 hours, then change at the wedding location. I'll have time to touch it up when I get there, but not time to do a complicated hair style.

Any ideas? Thanks!