To begin with, don’t conflate gender expression with sexual preference. Our culture does this constantly, whether in the assumption that princess boys will grow up to be gay or that women who are butch sleep exclusively with lipstick lesbians. Some of those boys will no doubt grow up with same-sex desires, and some women who refuse to wear skirts are queer. One does not lead to the other. While grown-up queers often retroactively identify nascent gayness in childhood gender rebellion (“I was never good at sports”; “I hated playing with dolls”) and the gender police often conflate gender non-conformity with queer sexuality, they’re two different aspects of identity and experience. Children negotiate gender roles from the moment of birth, when they’re assigned a gender and adults interact with them accordingly (see Fine and Rivers & Barnett in the reading list below).
Children are also sexual beings, it’s true, but sexuality in the adult sense is something we grow into. It’s a process. And presuming adult sexual preferences for a child — whether it’s teasing them about a playground “boyfriend” or assuming their gender non-conformity will lead to same-sex desire — is unfairly boxing them into predetermined categories. We cannot know what the gender and sexuality landscape will look like as they grow into adulthood, and we cannot know what words they will choose to describe themselves. All we can do is give them a multitude of words from which to choose.
You can check out the whole piece -- including my "suggested reading" list (I'm a librarian after all!) over at In Our Words.