Our family with 5 memebres want come to china and hongkong and how can i get invitation letter

We have 5 memebres in our family, But sri lankan embassy told us for the first time visitors to china need to get tourist visa for a 10 members group. But we want to come our own way with familiy members. How can we apply for visa and get the invitaion which is submitted to the embassy.
Wimal. sri lanka