Hi Linda!
First let me say that Narcoosees is one of the best dining options at Walt Disney World, so good choice there!
Second, I would try to time my meal so that you are actually finished right before or soon before the fireworks because then you can simply head out onto the viewing dock that is right outside the restaurant. It will offer a beautiful view without the proximity to so much noise.
Now, the next thing we need to figure out is what time the fireworks show is on the night of your preferred reservation. To find this out, log on to
www.disneyworld.com and click on Parks. Select Magic Kingdom from the drop down menu. Then click on Calendar, and choose the month you are visiting. Finally click on the specific day on the calendar and it should have the entertainment schedule listed. Just keep in mind that the park schedules typically show only 6 months out from the current month, so if your trip is later in the year, it may not be available just yet.
Once you see what time the park hours are for your trip, it will be easier to target a reservation time.
Please let me know if I can help further and I wish you a Magical trip!! :)
Chris