It’s a bit weird (and rude) for other parents not to respond back when you greet them. But I’m also a small woman who “blends in” (for lack of a better word) and doesn’t usually speak to others unless spoken to so I’m perhaps not the best person to give advice. (It does hurt, though, when I’m left out… which is why I tend to just keep to myself. Again, not good advice, it’s just a coping mechanism for me.)
I understand wanting to keep a good relationship with the other parents and I think it’s good to keep trying. Is it a mix of mothers and fathers who pick up their kids? Sometimes the moms aren’t so keen to speak to other fathers. Also, are the other parents friendlier with the international couple?
In terms of trying to get parents to open up, as an antisocial person, here are things other moms said to me that made me talk more:
-complementing my child on something, like her cute shirt or shoes
-mentioning that their child spoke about mine at home (I understand your daughter is still too young for that yet, but soon!)
-talking about an event coming up
I also asked my husband about this and he said that if they continue to be cold, you shouldn’t waste your energy on them…