Sexual orientation is not a developmental issue.
Children need to be taught early that they have a right to privacy. If they don’t want their parents to know something and no laws are being broken, there is usually a very good reason for it and the child’s wish should be respected.
In regards to being gay or trans in particular, you have no idea what kind of Pandora’s Box you’re forcing open there. Parents have flat-out killed their own children for being LGBT: http://www.cnn.com/2016/04/02/us/father-gay-son-murder-charge/