Dear Mr Kari,
Thank you for your invitation to attend your birthday party. However, I have to visit my grandfather in hospital on that day. I am likely not able to rush back on time to your place. As such, I am very sorry that I am not able to attend your birthday party. I had asked David to hand you a Chinese to English dictionary as my present to you. I hope you will like it.
Sincerely and have a happy birthday,
Li Hua
O(∩_∩)O哈哈~