Well, if the child wants to date and shows responsibility with it, I really don't see how it's a problem. It's their expression of love for someone else. I know, this is very cliche, but we can look at Romeo and Juliet (I am judging myself right now, don't worry) and see how limitations of dating has caused problems. I know, it's fiction, but I'm sure this happens (to a lesser extent) to people of different races, religions, or general backgrounds.
That's why I see a lot of people here saying they will share the implications of wearing a dress and tell them how society views these subjects. If they are aware enough, why not? I know children are seen as limited in the capacity of their understanding of the world, but there are others who really outgrow their size mentally and have a view on society that is actually profound.
I think it's baby steps. You can introduce it into the household, and see if they feel comfortable around the family, and then bring friends over and see how they feel towards their reactions. Doing it little by little, and not throwing them into the wild (schools or public settings) can help them adjust and see if they are ready for the choices they make. Autonomy is key in growing up. Not giving them full autonomy, but constraining them can stunt their development.
