Here are some suggestions of the best places for viewing the fireworks at Disney World
Magic Kingdom Fireworks
Main Street, with the castle in the background - the fireworks will be behind the castle (Your view of the fireworks will be restricted if you stand too close to the castle)
The bridges to Tomorrowland & Liberty Square - in these two places the fireworks will be to the side of the castle.
Tinkerbell will fly right over you if you are on the bridge to Tomorrowland.
Epcot IllumiNations
For a good view of the show you need to see both the centre of the lagoon & the sky. Wherever you choose to stand make sure the wind is blowing away from you.
World Showcase plaza is a great viewing spot, but you need to get there early.
In Germany, on the Friendship boat dock or waterfront.
In Canada, on the waterfront opposite the totem poles.
In Italy, on the waterfront near the gondolas.
In Mexico, on the veranda of the Cantina de San Angel.
The bridge between France & the UK.
Disney-MGM Studios Fantasmic
The best views of Fantasmic are anywhere in the central area, especially near the front.
In order to get a good seat you will need to get in line in good time.
A Fantasmic lunch or dinner package is available at Mama Melrose, Hollywood and Vine or the Brown Derby, which includes reserved seating at Fantasmic. The reserved section for Fantasmic is on the right-hand side of the theater.