I dont think there would be a problem with your PR processing times even if you have autistic child, i have seen many family with autistic kids got their PR almot same time as others
Would warn you to be prepared for very long waits to access services related to autism (years) and likely have to supplement any services you receive by paying out of pocket. Depending where you are currently living staying where you are or considering other countries may be a better idea if access to autism services is a priority.