I wouldn't pump and dump. Alcohol doesn't hang around in breast milk forever. It clears at about the rate it would take to clear your blood. Honestly, if you are sober enough to drive by the time you get home, you'll be fine to nurse. You are not going to want to go crazy drinking anyway. After not drinking for a year your alcohol tolerance is probably way down and you'll get buzzed pretty easily. Make sure you drink plenty of water before and with dinner so you're hydrated.
I always went by if you're sober enough to drive, it's ok to nurse guideline. But if you tend to feel a bit paranoid about these things, here's a chart to help you:
http://www.nfhs-pg.org/media/1_Prevention/alcohol_algorit...
Hope that helps! I hope you have a very wonderful evening out!!!!!