Schedule your dinner at california Grill on a night when there's Mickey's Very Merry Christmas Partry (
MVMCP).
Fireworks are usually at 9:15.
Try a 7 or 7:30 reservation.
That way, you'll be able to have a nice, leisurely dinner, and be able to either walk out on the observation deck, or sit at your table for the fireworks, if you have a good spot inside.
They do pipe the music from the fireworks into the restaurant.
On nights they don't have MVMCP, I think the fireworks are at 6:00.
I prefer the later start time for the fireworks if I'm dining at CG.
By the way, those volcano pork egg rolls as an appetizer are really, really good!