I eat at Narcoossee's during every trip. You may want to see if you can change your ADR to 8:45 or even 8:30. Your best bet with the fireworks, regardless of the reservation, is getting there early and not worrying about being too close to the glass. People almost always crowd in front of you and it's hard to see anyway. Have the staff hold your next course (they're used to this) and go outside on the deck to watch with the rest of the patrons. There is a crazy amount of bugs, so try and avoid being directly next to any of the lights. They turn them off, but the bugs stay around them for the most part.
Being a chef myself, I can tell you you're in for one of the best dining experiences The World has to offer.