If memory serves me, the pre-Vatican II Catholic Church solution in many parishes for children who might cry or otherwise disrupt and distract the congregation during Mass was the crying room. This glassed room, in the church proper, offered full view, audio and chairs that allowed parents and their children to be at Mass together and yet not drown out the service with crying and tantrums. (I am certain a bite or urinating took place in there, and probably some kids hitting each other, too.)
I am not quite sure when the crying rooms were phased out, but perhaps it is time to bring them back.
Surely that would be kinder than banning an autistic youngster from attending Mass.
