That is not a smiling child. He is grimacing in pain and fear. Note the knotted forehead, the lower teeth exposed not the upper, the teeth clenched, the lips are stretched out but not upward, the cheeks are not raised to narrow the eyes as in a genuine smile.
All that in response to "say cheese"?
I think you may be right. When I first saw it, I thought the boy in post #28 was giggling, smiling a happy smile. But, then I read your post and leaned my head to look at his face from a different angle, and his expression does look more like a grimace, or like he’s crying. The photo is almost like an optical illusion.