Each park has areas roped off where wheelchairs and ECVs are allowed for viewing parades. You can see these locations by getting the maps available at each park. The areas are not large and there is more than one location in each park. All the spots are on a first come, first serve basis. These areas tend to be very crowded and they fill up fast.
Epcot has special areas for fireworks. Again, refer to the map for the locations.
Keep in mind you can be anywhere in the parks for viewing; you are not limited to the handicap areas only.
So true. I went for convenience and booked the firework viewing party at MK (Dessert Party) and at Epcot (Illuminations Sparkling party) so that my best friend (who will be in a wheelchair) would be able to have the best view possible. This may not work for everyone cost-wise ($$).