I wouldn't exactly consider Sardi's or Russian Tea Room as after show "dessert" spots.
A couple of questions:
are you doing matinee or evening show?
are you staying in Manhattan or is it a day trip?
will you have transportation or are you relying on NYC subway?
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.
When it comes to "dessert" in Times Square, nothing beats Junior's in Shubert Alley. World famous cheesecake, nice burgers, sodas, etc. Not to mention a friendly, nice bar.
I don't know how feasible a group of 30 would be. . . . The place is large, but not that large. Then again, if you come late in the spring, they have the patio open. Maybe they'll be willing to seat you all there.
Then again, with the economy these days, I'm sure they'd be thrilled to have you, regardless of the size of your group.
When you decide on a place, I would call them a day or two ahead and give them a head's up. Many places may find it difficult to handle that many people.
If anyone ever tells you that you put too much Parmesan cheese on your pasta, stop talking to them. You don't need that kind of negativity in your life.