One possible version :
Dear _ Mike, _
I'm _ glad _ to _ know _ that _ you _ are _ coming _ to _ China _ with _ your _ parents _ and _ spend _ the _
MidAutumn _ Day _ here.
The MidAutumn Day is a traditional festival with a long history which is celebrated only by
Chinese people.It falls on August 15th of the Chinese lunar year,when people of a family get
together and enjoy the dinner together.After that they eat mooncakes,which stands for the spirit
of the festival-unity.Often,if the weather permits,they will go out of the house to enjoy the bright
moonlight,talking about something pleasant.It is one of the most important festivals for Chinese
people.
I wish you a pleasant journey and I'm sure you will like our traditional MidAutumn Day.
Yours,
Li Hua