Dear Amie,
This letter is to invite you for my father's 5Q*h birthday. We are planning a surprise birthday party for him on 25th June.
I am informing you early so that you can make your plans accordingly. We wish to see you as dad always talk about you and he is very fond of you, he will be glad to see you on his birthday.
We are planning his party at our place. Please do not mention anything to him, when you meet him - it's a surprise birthday party for him. Hope to see you soon.
Regards,
Stacy