Hi, Linda!
I have a few favorite spots for viewing holiday fireworks at Magic Kingdom, and select according to who is with me at the time.
If only adults are in our party, or children who aren't so little that they're in strollers, I like to stand on Main Street U.S.A., where it opens up in front of Cinderella Castle. If you can position yourselves so that you can see the Castle, you'll be able to enjoy whichever laser show is being projected onto it for that particular season. You'll also have the perfect perspective for capturing photos of fireworks and shaped fireworks as well (stars, etc.)
On the other hand, if there are those in your party who cannot stand for that long or who might need a break, but don't mind not being able to see the entire Castle, grab outdoor seats at Casey's Corner, right up front at the railing which edges the grass and flowers. Enjoy some excellent corn dog nuggets or cheese fries and a refreshing beverage while the spectacle unfolds before you. So relaxing!
Finally, if you have little ones in your party, and need to make a quick exit after the show, we like to sit right in front of the Main Street Train Station, or right at the railing on the second floor of the Train Station. This way, once the last spark flies, we can be among the first Guests to leave the park, helping to ensure that we'll be able to catch the first or second bus back to our Resort.
Check out this
map of Magic Kingdom to locate these locations prior to your trip. Any of these will afford you a great view of Cinderella Castle and the fireworks above her; just pick the one that suits your needs and enjoy!
Send more questions as you think of them, Linda. We love to help!