What I'd do is after the O show ends, go to the back of the Bellagio by the pool area and there is a gelato shop. Get some gelato and head out outside by the pool and sit on the benches they have there. It's pretty neat at night.
Or, if the fountains are still going, take your gelato out front and watch the fountains.
I agree with the poster that said the good restaurants will all be closed by midnight. If they're not closed, they probably won't want to open up a new ticket anyway.