Those advocating that men, transvestites, or trans should be able to access women's personal changing areas, because they have self declared.
Would you want your wife and or daughter in close proximity to a fully intact naked male changing alongside your child, spouse?
I think you're trolling here but we're talking specifically about trans women. If you bother to read up on the subject Self ID is about how, as a trans person, one gets legal recognition of the fact that you've changed from the sex/gender allocated at birth to another. It is, at best, peripherally relevant to accessing women's changing rooms or toilets etc.
My wife has seen fully intact naked males before, my daughter too - she's 30. As one of my wife's Grannies used to say; If they can see anything they've not got they can hang their hat on it'.
A younger child will ask questions about why there's somebody over there with both a willy and boobies. Just as they'll ask how the baby got into their friend's Mummy's tummy.
Rather than waving your petticoats in a panic just give an age appropriate answer.