Brunch in Durham, NC
I'd have suggested Dame's Chicken and Waffles but can't do 12 without a heads up. See about Parker and Otis. Everything is fairly close in downtown Durham. Another good option (esp if it is nice out) is to go early to the Durham Farmers Market and hit up the food trucks and baked goods or grab some items from Daisy Cakes as they may be able to seat you all outside if that isn't a problem. Just a thought.
Old Havana Sandwich shop is only a few blocks away--very casual, large sunny space. Sometimes it's difficult to find parking.
Otherwise, any place in Brightleaf is not too far, with plenty of parking. I recommend Parker and Otis or Alivia's. You probably won't need reservations at any of these places, but I guess to save time you should give a heads up to Alivia's that 12 people are on their way.
I second the Mellow Mushroom recommendation as well.
Next to the DPAC is Tobacco Road, a sports bar. And at the DPAC, you'll be right next to American Tobacco, which has Mellow Mushroom (a pizza restaurant) and Tyler's (American bar food). All of those would be good for your group. I don't know at what time any of those places open. With a group of 12 and show tickets, you probably need to make reservations, but I don't know if any of those places take reservations.