[hutzlibu]

Depends. It is not a single coherent ideology. Most anarchocapitalists regard property and property of ones own body to be sacred. That would disallow selling children as you cannot own them in the first place. They own themself.

[fluoridation]

That would mean you can't sell children as slaves or meat, but not that you can't sell custody of children.

[hutzlibu]

Good observation, but depending on the type of anarchocapitalists we are talking about, there might not be such a thing as custody.