Whatever it is, it better be 'scope and 8-channel HD audio.
Here's Blu-ray.coms list of BD with 7.1 audio. http://forum.blu-ray.com/showthread.php?t=159814
Among the newer stuff, Mission Impossible: Ghost Protocol, The Bourne Legacy and Prometheus look like good candidates. Lots of newer action-type movies that I wouldn't choose for myself, but you might - The Expendables, The Hunger Games, Abraham Lincoln: Vampire Hunter, The Avengers. LOTR trilogy, Star Wars, and Top Gun all have 6.1 HD tracks, and are 'scope - Good choices, IMO. For older stuff, you don't find much 'scope, but still some great options. E.T., Cinderella and Dumbo - 1.78 and 1.35 respectively, The Sound of Music is 2.20. Dances With Wolves is 2.36, but not a lot of fun for a premiere. Maybe Jurassic Park?
For me, from this list, I think I would go with one of the first three - maybe the shortest in run time, just so that you can spend more time with the lights on talking about the cool new theater you have. Actually, I think I would go with Top Gun or Star Wars (IV) - I'm a sappy sucker and those are classics for me.
Congratulations on the premiere!