I start this by saying I do not proclaim to tell anyone how to raise their child. I am not a parent. That being said, this is a questionable move.
The main argument young Sasha's mother brings is that she did not want to enforce stereotypes upon her child. While that is admirable, does gener identity in itself suppose stereotypes? Couldn't it be just as easy to tell the child he's a boy and then let him decide for himself what that meant to him? Children have questions about self discovery and there's only so much not answering a parent can do.
Adding to the confusion is that the couple have two older children, giving Sasha both a brother and a sister. Have they seen adverse affect of gender roles in them? Do they feel cheated for not having the oppretunity to choose their youngest sibling has? This isn't brought up.
I guess the big question here is how much do you think that gender roles affect children and how you would approach this situation. Their forbadence of skull prints shirts gauls me as a Punisher fan but I can see it not fitting a 5 year old.