If your seated during the firework show they dim lights and pipe in music. If you eat before the fireworks save your receipt and they'll let you back into the lounge or onto the observation deck to watch the fireworks. (As long as there isn't a special celebration at the time.)
we were between dinner and dessert when fireworks started. we did not have window seats but could certainly see the castle. DH took boys and went out to that patio/walkway area to watch (music piped out there as well) and DD and i stayed in and watched.
hoping to make it a "last night" tradition, we loved it so much!!
Also depending I guess on how busy they are, etc. you can have what you think is an early reservation and the waiter will try to stretch it out so you are still seated for the fireworks. This happened to us in December. The waiter was super sweet and wanted us to take our time so that we could be there for the fireworks. I finally told him I really appreciated it but we had seen the fireworks five times already that trip and really just wanted to eat and go back to our resort.
We ate there last week and our adr was for 7:25pm. We finished dinner about 8:45 or so and our waiter told us we could hang out at our table or go on out to the observation deck. We chose to hang at our table a bit and went out about 5 min before the show started.
3 weeks ago our adr was 7:25, and it worked out perfectly. We were just finishing up dessert at 9. Be sure to let them know if you are celebrating anything when you check in. We were celebrating our youngest graduating from college, and the waiter brought us free champagne before we ordered dessert!
Dinner at CG takes about 90 - 120 minutes so we make our reservation about 60 - 90 minutes before fireworks. Sometimes we are finished dining before the start of fireworks, but most of the time we are between entree and dessert. We let the server know we would like to go outside to see fireworks first and that we'll have dessert afterward.