Live The Message
I would go and be my usual 'put up or shut up' self. I would not drink before or during the Concert.
For me, it's a little disingenuous to pitch the message 'Hey, Honey, you can enjoy Life without Alcohol', and then go to a Concert and have to drink. Sure, it's an option. But, is it an option that has to be exercised that evening? A mixed message there, and perhaps not the intended one on a visceral level.
One-on-one, I would let my Spouse know in advance that I won't be drinking; solely with the intent of being proactively supportive. If she would take advantage of you remaining Sober during the evening [I've been the DD in the past quite easily], and drinks because your're suddenly an alternate DD, a larger objective has been achieved. You'll see first hand how she's coping with Recovery. None of this will be a bummer of an unexpected surprise because you will have managed and processed up front the several possible outcomes. For me, this would allow me to enjoy the Concert without the futile effort of attempting to control the behavior of someone else. Go. Detach. Enjoy.