You want to take your child to the local precinct office and introduce them and their disability to officers in a calm setting
This might work in a smaller town, but this family was in LA. I’ve never lived there, but I have lived in NYC and I doubt anyone in the precinct would care. They would just file some paperwork and move on to the next thing. There’s probably less than a 50/50 shot that the paperwork would be communicated to any officer in a crisis. And back when I lived there in the stone age, that chance would have been zero.
Maybe if your precinct does community policing, it would be beneficial to introduce yourself to any officers you know are local, but that assignment can change on a whim.