It depends on which building you get - they surround a small lake on all sides. If you're in a building on the south side of the lake, then the lake view rooms on higher floors will look out at the lake with the Epcot fireworks beyond the trees. If you're in a building on the north side of the lake, then the parking lot view rooms on higher floors will see the Epcot fireworks beyond the trees.
When you make your request, just ask for an upper floor room with a lake and fireworks view. Remember that requests cannot be guaranteed and owner requests are filled first. They do try though. If your room doesn't have a fireworks view, you may go to an upper floor of a building and watch from the corridor windows by the elevators. I've read that some of the higher fireworks may even be seen from pool area #2, the one with the slide on the SSE edge of the lake.
