Wheelchair area/fastpass/DAS for parades, fireworks and shows

[Palm trees]

Sorry for such a long thread title but I think it's all related. We will be entitled to the DAS (have used it before) for our son who has both a learning disability and a (more minor) physical disability. He is a wheelchair user but can walk, the distance being dependant on energy levels and frame of mind. I know people are recommended to get a space early for a good view at parades or fireworks but our son would not be likely to understand the need to wait/potentially struggle to cope in the crowds for an extended period as he will not necessarily grasp why he is waiting (he can sometimes struggle a bit with ride queues but at least while we keep moving he manges better). We have yet to watch any of the fireworks and have avoided parades on previous visits but would really like to try them on our next trip.
My questions are:
Are there wheelchair areas at all, parades, shows and fireworks?
If yes do you need to use a fastpass or das to guarantee access without waiting too long?
Basically what is the best way to manage these?
Thanks in advance if anyone can help or offer a view.