How will Laila's lying to her son affects him when he knows the truth?

I really don't know. In a society like that, some males are effectively conditioned towards a type of theological and social misogyny. It all depends what age the son is how he processes the idea. I would imagine that Laila would not fair well. I think that if her son has his mother in him, he will understand why she lied to him. If he becomes brainwashed by the Taliban, he might not understand.