Probably but consider where you are going to put the bag because chances are the seats next to you will be occupied
The diaper bag wouldn't be a problem, but they do inspect bags now. They technically don't allow outside food/drinks, so you would need to contact the box office for confirmation.
Yes you can i put mine under my chair during the show. I can't remember if the restrooms had changing tables or not.
Seating is very tight. Keep that in mind.
As long as the sippy cup is empty you shouldn't have a problem. No outside food or drink
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