Where is the line? in Journal

I’m told that it’s impolite to talk about religion or politics with family. So we can’t talk about anything important. Who exactly to talk with about thing of importance? Or maybe we’re just not smart enough, as normal people, to have thoughts of significance?
That’s what it sure seems like.
This weekend I had dinner with my bf’s parents, his brother, his brother’s gf, and his brother’s 15 month old son.
I’m not a talkative person; mostly I’m reserved, observant, and keep to myself. But there’s times when I wish I could say things that socially, might stir things up.
My bf’s brother and his gf’s son is 15 months old and doesn’t say a single word. Walks a little but, but not good balance. He won’t look at anyone. He stares at spinning objects; he is fascinated by them. He doesn’t interact with anyone in a meaningful way. He’s always got this slightly concerned, uncomfortable look on his face. I’m here to tell you, that the kid is very likely autistic.
I know this, I can see it miles away because of my health and research background, but here it is staring me in the face in family life. What am I to do? Ask if he’s been tested? Suggest that maybe an evaluation could shine light on why he’s so distant? While I’m mulling it over, Mom is feeding him Cheerios and pasta. ugh. She talks incessantly about his life. It’s a little exhausting to listen to, and I kind of zone out whenever she starts.
And I’m sitting her wondering if she has any clue; does she know what is in that box that she’s feeding her son? Is she aware that the earlier a child is diagnosed, the better the prognosis can be? Would it be completely out of line to suggest feeding eggs instead of extruded corn/soy circles? My intentions are nothing to do with judgement; merely a communication of information. If I could write an anonymous letter, that would work just as well if Mom would take it seriously. It would be worth it if the child was able to get diagnosis and a treatment plan in place early.
I feel at a loss. I just sit quietly instead. I don’t have kids. I don’t really know what it’s like to have one. But I bet it’s a lot harder if the kid ends up autistic.