Yes and no.
Narcoossee's is at "street level" so you can stand outside the restaurant and watch the fireworks later in the evening.
An earlier dinner's receipt will not get you back on the inside as CA Grill does.
It's not like CG. You don't even need a dinner reservation to watch fireworks from the boat dock near Narcoossees or the marina viewing area near Gasparilla's.
You won't be able to see the projections on the castle regardless, but it can still be fun.
Views from inside the restaurant can sometimes be obstructed by viewers outside anyway, so I wouldn't recommend that in the first place.
Be sure to check and see if if GF band or pianist is performing that night. You might have the option to enjoy some relaxed entertainment in between dinner and fireworks, depending on the timing.
You used to be able to watch from the veranda, however you are no longer allowed if you are not a patron. I would ask if I could return though, it is lovely and the music is easily heard.