Hainan Island Visa free process

Hi again,
I have an Australian passport. I will join a 5-day Hainan tour in Hong Kong and know that I don't need to apply for a Visa if I fly directly to Hainan Island from Hong Kong.
Do you know if I need to provide any documents showing the itinerary including air ticket booking record (round trip) and proof of a hotel reservation, etc when going through to the customs please?
Or do I need the travel agent in Hainan Island to inform the customs in advance please?