Senzhen from HK group visa

Hi, I'm from Indonesia. I learn from a milist that if we go to Senzhen from HK more than 3 people, we can go to Senzhen by Free of charge "Group Visa", if we visit not longer than 6 days stay.
1. Is it true ?
2. If it's true, how and where can we get the free of charge group visa ?

note : I plan to take a day trip to Senzhen from HK with my families. We are totally 8 people.
Thanks.