Travelling as a family of 13 to Haikou this December 2016

We are all from Malaysia, we will meet up at HKG airport and depart to Haikou with the same flights. Our Malaysia tour agency have inform us no need visa for visit Haikou, I do also ask them do we need any documents to show to china custom during our arrival, but my travel agency said no document needed, just show them our passport.
It is true? Can you please also let me know what is the procedure we will go through once we arrive Haikou airport. I'm too worry, afraid that we are not allow to enter Haikou. Thanks