The OP is talking about very young children. Specifically, children so young that they don't have a meaningful choice about what clothes they wear.

I'll talk with my son about the possible existence of latent sexism in society and how he might react to it when he's old enough to understand. Since he's not yet two, I limit myself to not freaking out if he picks up and plays with a doll.

Why would I want my daughter to work hard at math and then miss a job offer to do math because a competing interviewer was epsilon better turned out?

This is a false contradiction. It is totally possible to dress well as a woman without being "girly" or "sexy." To the extent that woman are expect to put effort into dressing "feminine" when men are not expected to put in similar effort to appear "masculine" in order to achieve the same success, this is a bug and not a feature.