Personally very excited about Tuck from I've seen and heard, and I can see it working well if you're going with a group with many generation.
That being said, I would second She Loves Me, and to a lesser degree, The King and I. They are both classics with beautiful productions and a great cast.
I didn't love School of Rock as much as some other people did. Yes, it's a cute story, and the kids are crazy talented, but I didn't love the music and I just liked other shows better.
I would also recommend Bright Star though. I thought it was a very moving story, with a great book by Steve Martin (perfect balance of emotional and funny) and very good blue-grassy music. I'm not in country music at all, but this was great, and I can see it having an appeal to wide range of ages.