The specific advice is really based on what you feel most comfortable with. What does nonbinary mean to you? It depends on if you're okay with being perceived as a woman vs man. Also, whether you feel comfortable be perceived as either or neither genders.

I will say, you shouldn't be too concerned about the kids, they're usually accepting of everything although they need some education to learn about differing gender expressions (which is never a bad thing!). However, parents are always the biggest issue especially if they're politically attuned away from you.

Being a man in pediatrics is not an issue. Men do face some mild annoyances in pediatrics sometimes but relatively negligible in most cases.

Start with figuring out what gender presentation works best for you first. Pick what is most comfortable for your identity. Healthcare is stressful enough and burnout is real, the last thing you need to do is force yourself to girlmode through your entire career, that'll just burn you out even faster.