
You can find the handicapped viewing areas marked on any park map. They are marked with a wheelchair symbol with a big letter 'I' next to it. Here is a park map detail where I marked the areas with a blue star.
In all of the handicapped viewing areas for parades in other parks or Illuminations for Epcot, mobility devices are lined up very close together (almost touching) across the front of the viewing area. Typically, there is not space for a companion to stand next to the mobility device; there is space for one companion to stand right behind and the rest of your party behind that person.
If the area is not full, there is more space and you be able to have at least one of your group next to you. If more guests using mobility devices show up (as happened with Toffeewoffy), those guests standing along the front are expected to move to make room up front for the mobility device.
Our experience has almost always included being told that information at the time DD was given a spot for her wheelchair.
Most guests are understanding, but some occasionally refuse to move.
The only viewing places that have totally unobstructed views are in the Showcase Plaza area. Because of that, those are the most crowded areas and it is not uncommon to have 2 or even 3 rows of mobility devices. Many people also want to be in that area to be able to leave quickly after the show.
I would recommend NOT trying to leave until the crowds thin out, which usually takes about 10-15 minutes after the show. If you leave right away, you will be walking out in heavy crowds and packed buses. Waiting a bit allows for walking out comfortably and the bus might not even be full.
The space in Germany is the one we most often use. It's not huge, so may fill up. Whatever area you use, plan to arrive at least an hour before Illuminations begins.
You can park an
ECV along the fence by the water anywhere around World Showcase. The closer you are on either side to the Showcase Plaza area, the busier it will be.
You can also look for spots as you walk around during the day. The area where the globe is on the map will be about where the globe will be during the show.