To sleep together is a euphemism for having sexual intercourse. Using euphemisms when teaching children about where babies come from can be dangerous. There was once a young girl who was afraid she was pregnant because she and her boyfriend fell asleep watching a boring movie. She did not know how baby-making was actually done and had only been told the euphemism. So she went and told the school councillor that she was pregnant.
Her story is innocent, although scary for her. In a different case, a similarly innocent girl, did agree to have sex with a boy. However she would not sleep with him because she was told that good girls did not do that. In both cases the child has confused the same adult euphemism for an actual fact.
Public libraries have children's sections and adult's sections. However when selling or renting movies the word adult is used as a euphemism for movies with naked people in them. People have innocently walked into the room where the adult movies were being sold without expecting to see naked people on the covers of the VCD cases.
After a funeral, a child was once told that her grandmother was now one of the stars in the sky. (This was in a small town in the US, where unlike in Hong Kong many stars can be seen in the night sky.) Afterwards she would look out of her window at night and talk to her grandmother. The story sounds cute and is much less traumatic, for the adults, than explaining about death. It was not less traumatic for the girl, or her science teacher, when he taught his class basic astronomy.
We need to be clear when teaching children and second-language learners. To do this we must avoid euphemisms, unless we know that the meaning has been taught. We need to communicate clearly and being overly polite can limit our ability to be understood.