Yes, listen to zebra and me, NOT PETE, and be sure if you're going to ask her in front of a large body of people, she won't be too embarrassed by it (is she shy?), and that she won't feel compelled to say yes just because of all the people looking on, meaning be darn sure she'll
want to say yes. But, otherwise, I think in front of the graduating class would be absolutely awesome! Definitely a day she would never forget.
Or, if you like, you can go with Pete's bitch slap approach.