The
California Grill is a great date night spot. The food is wonderful, there is an amazing wine list, the service is sublime and that view just can't be beat. There are some sort of fireworks at the Magic Kingdom almost every night of the year. To find out when they're happening go to the Disney World calendar
HERE. To see when the fireworks are click on the numerical dates on the calendar. For example, if you click on October 27, you'll see that the Wishes fireworks show will be at 8:00 that night.
Because of the dates of your travel, you are going to run into a minor problem however. On October 26, 28, 30, and 31, you will not see Wishes listed on the calendar. That's because these nights will have Mickey's Not So Scary Halloween Party at the Magic Kingdom. There will be special fireworks for the party, and these would be lots of fun to watch from the California Grill, but unfortunately the exact times of those fireworks have not yet been released. You could estimate that there would be at least one showing in the 8:00 to 9:00 range, but that is not confirmed yet.
If you are interested in dining at the California Grill, I would call Disney Dining at 407-WDW-DINE immediately as it is likely that many of the reservations have already been taken. They may also have more information about the Halloween fireworks.