hiya
not sure on the helper gfetting in free - i wud assume that u wud have to have a blue disabled badge for that (needing help with mobility).
as for all other types - yes, go to city hall with proof of disability, and they will give u a easy access card.
it doesnt always give u straight on access to rides, sumtime u have to go and come back at a time, but others u get straight on.
there are also spots roped off for parades - but i wud say - as u mention spectrum disorder - that it depends on the disability as to what u use, as sumtimes it is easier to not use it!
hth