On the one hand, we have those such as the Bangkok Atheist, who recently proclaimed that people “do not choose their gender” but are born with it, implying that men who behave as women are predisposed to do so.
Then on the other hand, we have those such as Nigel Pike, who believe that people born with XX chromosomes are naturally inclined to behave as women, while people born with XY chromosomes are naturally inclined to behave as men.
The Nature vs Nurture debate has raged on for a long time, but it must be pointed out that a satisfactory answer has yet to be found.
Anyone who proclaims that they know the answer is patently wrong. The fact remains that medical science does not really know if people are born gay or choose to be so.
Thus the best course of action, I think, is to encourage your children to behave in harmony with the chromosomes that they are born with. Encourage boys to behave as boys, and encourage girls to behave as girls, and if they act otherwise, then give them all the love and support necessary for them to get on with their lives.
Life as a gay person is a difficult experience, and even here in Thailand I have noticed that people often treat ladyboys as clowns, and that employers outsides of Pattaya and Phuket are hesitant to hire them. So living life as a gay or lesbian is not something that one should just casually do.