At primary age I would not have wanted my children to be introduced to gender/transgender topics, not least because it implies gender stereotypes, plus there is a reasonable likelihood that a number in each class will go through a period of uncertainty about their sexual (or perhaps even gender) identity during adolescence and given the risk of contaigon I would want to understand what the school planned to say. I would have wanted a much more shallow approach that people can be different and that acceptance is important.
It is easy to get it wrong. When DC were young there was a big debate about how much children should be taught about the Holocaust and at what age. The school preferred to leave Anne Frank etc to years 5 & 6. However as a compromise a mother was invited into reception to talk about Judeaism. Cue DD coming home in tears. She had no friends. Why? Because Jewish people don't like non-Jews. Who knows what was said, but I assume that was not the intention. Similarly a friend's kids, who attended a seriously multiracial primary at a similar age came home saying they had been taught they had to be nice to children who were a different colour. But they did not know any kids who were blue or green, just ones who were varying shades of brown or beige.
This incidently will be problem in many south London schools where there is an obvious and immediate culture clash between liberal ideas and evangelical teaching. Which is probably part of the reason why evangelicals have moved into running Academies, much to the distress of some parents whose children have been allocated places at them. But then my guess is that the GC debate will start to gain traction when and only when culturally conservative groups start to protest.