Dear Father,
I just got my letter from Hogwarts. Harry is taking James with me to Diagon Alley to shop for my first ever school supplies. I wish that it was you holding my hand in the crowded streets filled with all the other young wizards and witches. Still, I know that you are always there with me, even though others might not see you.
A few days ago, Harry broke to me that you were a werewolf. He said it to me in a big rush and then turned away quickly, I think he knew that he had just violated a secret you had entrusted him with. But he also knew that I had the right to know. I am not embarrassed or ashamed like Harry said you thought I might have been. I think that makes you an even cooler Dad.
I wish I could talk to you in person. I know we would have gotten along so well. Your visits in my dreams are not enough, because dreams are not real. I sometimes wish I could swap with James, just for a day, so I could get a taste of what my life could have be with parents. A godfather relationship isn't the same.
Your Loving Son,
Teddy.
AN: Thanks to Immortal Fallen Radiance and Ralinde for giving such useful feedback for this. I have edited it now - hope it is better!