I am curious about this same topic as well. I am considering the same strategy for our trip next year. I have one DD on the austism spectrum. The GAC worked wonderfully for our family at EPCOT. However, on our next trip I would very much like to see Fantasmic. My fear is that the crowd that gathers for the show is enormous. I have never seen the show but I have read enough reports about the huge crowds that make me reconsider seeing it. It is not so much the waiting to get in that scares me most. It is the exiting the show that has me mostly worried for my child. I remember what it was like just leaving EPCT after illuminations. The crowd was huge and it was dark. These are two factors that cause a lot of anxiety for her.
I have read/heard that the second show (if there is a second show) is always better in terms of crowds. Maybe this is the better way to see the show regardless of the GAC.
If you try to leave right away after Fantasmic, you will find the same 'mob' of people leaving that caused problems for your DD when leaving Epcot.
My advice is to stay seated until the majority of people have gotten up and left. Even 10 minutes makes a BIG difference. That is what we always do. After most of the people have gotten out of their seats, the CMs will come in to pick up trash before leaving in the guests for the 2nd show (if there is one). So, you don't need to be in a hurry to get up and out of there. The CMs will be cleaning for a long time after you have left. And, instead of leaving in a huge crowd, you will be leaving with a manageable group of people. If you catch up with a crowd, or a crowd catches up with you, just hang back for a bit and let them pass.
That will also mean that the first bus or 2 will have left; our experience is that the people rushing for the first couple of buses are the most anxious to get out and your bus (or parking lot tram) experience will be more enjoyable if you just let them get out.
Do the same thing for Epcot after Illuminations. Hang back and let the first guests leave. The largest concentration of people is at the entrance to World Showcase because people feel that is the best view (plus closest to the exit after the show), so we avoid that area. There are many good viewing spots around World Showcase where you will have a LOT less people around you. The fireworks barges are moved into place by mid-afternoon, so if you scout out an area with a good view of those barges, you will have a good view of the show. (Don't look at where the globe is, that will move out by the barges during the show). The only other thing to be aware of for Illuminations is which way the wind is blowing. If you are on the wrong side of the lagoon, smoke will blow at you.
When leaving, just stay put and let the crowd pass you. It will still be dark, but you will be moving out in a small group (sometimes the closest person to our group is more than 20 feet away). Without the large numbers of people, your DD might enjoy seeing the lights in each individual country. And, as you walk by Innoventions West, just after you cross the walkway between the Character Connection building and Innoventions West, stay on the pathway to the left instead of following the main path that goes out past Spaceship Earth. You will get a surprise with a really cool light show shining right out of the sidewalk under your feet.
Our experience at Fantasmic in October 2010 was pretty much the same as the copied part that LockShockBarrel posted. We arrived about 7:10 for the 8pm show and the crowd was already going - when we joined the crowd, it was just after the street between the entrance to Beauty and the Beast and the shops before that. It was not a 'tight' crowd, but quite a bit of space between people.
As we got close to the entrance, CMs were telling people that it was standing room only. DD was in a wheelchair; I also had her GAC in hand to show the CMs, but the 2 CMs we came to did not want to look at it. They just said to stay to the right (so very similar to the copied and pasted information).
The problem we had was at the point where guests with special needs wait to be seated. That was quite crowded and we had to wait there. It was also between the upper entrance to the dinner show and a souvenir booth, so we had constant traffic across our line. It actually was less busy where people were just going in without waiting for the special needs area.
When we came out, before leaving the Fantasmic area, we passed the guests who were waiting at a roped off area partly into the Fantasmic entrance. There was no special line for guests with special needs that I saw in that area and I did see guests with wheelchairs and
ECvs mixed in the line. After that point, our line veered back toward Tower of Terror and we came out a gate by Tower of Terror's exit, in front of the gift shop. We walked past the Fantasmic entrance, where again, I did not see any separate line/area for guests with special needs. By the time we got to that area, it was well after 8:30 and they had not started letting guests for the second show in yet. The line was all the way up Sunset Blvd to be even with the Villains Shop. It was wide enough that it took half of the street and was separated from the rest of the street by ropes. Since they had not started letting people in yet, the crowd would be big - that many people might not fill the show, but would temporarily fill the waiting area.
