Dear Sir or Madam:,
My family and I want to take a trip this summer ,but I have to face some difficulties.
There are many members in my family grandparents father mother children and I we all have different hobbies.Grandparents like games which are peaceful and the destination shouldn’t be too far .while my father is fond of thrilling and hiking but my mother disliking flying .Besides this trip had better give children some knowledge . In a total the perfect trip is that let us all enioy ourself.
Can you give me some advise .Thank you very much .
Yours ,
Lihua

1、开头称呼，把冒号去掉，英语中是不存在这个标点符号的。“Dear Sir or Madam，” 即可
2、每段开头空两格
3、没断句。There are many members in my family.Including grandfather,grandmother ,children and I .下一句可以。
4、“my father is fond of thrilling and hiking”这句不知道你想要表达什么意思，但是thrilling 是形容词，hiking是名词，不并列，不能用and连接。
5、besides 后面加逗号
6、all enioy ourself 单词拼错。是“all enjoy ourselves”
7、advise，可做及物动词和不及物动词，应改为名词“advice”
8、既是书信，应有日期

暂时这么多了