How do I get my parents to let me go to a concert?

I need to convince my parents to let me go to a Widespread Panic show down at the beach but I don't know how. Well I got into a little trouble a month ago, had a little too much to drink. Before this happened I promised my friend a ride with my sister and I. I don't want to look like a flaky who doesn't follow through. I have my tickets and the concert is in about three weeks. What do I do?