Teddy bears may be a convenient medium as they're androgynous. Good thinking, actually. If I was 11, though, I'd have a few questions. "How can a boy be a girl?" would be a start
And, no, I wouldn't be fine. If the narrative is "let them decisde for themselves...", then let them. How does this help one to "decide for themselves", especially as mom and dad are being excluded from that conversation more and more?