Dear Mary,
Thank you for your invitation. I’d really love to,but I’m afaid I couldn’t. I won’t be free that day. First,I will take part in the English contest in the morning. Then ,I will go to the Football Club in the afternoon. Finally, I will go to the cinema with my aunt in the evening. She just came back from New York a few days ago. And she will leave for New York the day after tomorrow.
I wish you a happy birthday.
Mike