Civilities: Do I introduce my child as my transgender son or daughter?

Dear Civilities: I have a lesbian daughter who has just come out as a transgender man. I will be introducing him as my child in our city's pride celebration later this summer. How exactly should I do that? Do I say: "This is my transgender son?" or "This is my transgender daughter?" I'm sorry if I sound confused, but I want to make the correct introduction to my friends that also have gay children. -- Name withheld