You mean "ejaculates into him".dislike Political Correctness so I will be blunt: in their bedroom that transgender woman (who still has a penis) penetrates that transgender man (who still has a vagina) and ejaculates into her.
Children will have to understand theif parents are special , different.
Children can understand that very well on their own. It's always adults projecting their fears and anxieties onto children. People don't even like to hear about their parents having sex usually, so why would they care about the finer details? Should parents tell their kids exactly what position they were in when they conceived, too?