train ticket for australians

Hi,
I would like to buy first class ticket for 2 australian passports from hong kong to guangzhou on the 22nd of october. Do i need a chinese visa to do this?
i also need 2 first class tickets on the fast ride from guangzhou to Shenzhen at around 6am
and lastly at around 4pm 2 first class tickets on the fast ride from shenzhen to hong kong

please advise if i need a visa first thankyou