Some girls might be a bit shocked at first. But then, most of them would probably be very accepting. They could start asking the crossdresser about their outfits and where they get their inspiration from.
Some girls might become more confident in themselves. They see it as a step into adulthood and a new phase of life. They start to take more control over their sexual health and relationships. For example, a girl could start to educate herself more about contraception and healthy relationships, feeling empowered by her new experience.
Some boys and girls might become withdrawn. They could be afraid to express themselves around their mother after being spanked. For example, in some stories, the child would avoid eye contact and stop sharing their feelings.
Well, El Cid has a basis in history. Rodrigo D铆az de Vivar was a real person, but the stories about him have likely incorporated fictional elements over time to make them more captivating.
The boy could react in different ways. At first, he may be shy and keep to himself. But as the girls start having fun, he might loosen up and start laughing along with them. He might also feel a bit awkward when they start talking about girl - stuff like crushes, but he could still be polite and listen.