Is my visa is allowed for a trip Hk-Guangzhou-Hainan-Guangzhou?

Hi am from saudi arabia and i have a one entry visa to go to guangzhou and iwould like to visit hong kong and hinan Sanya island so can i go to hong kong than guangzhou for four days than go to hinan finally come back to guangzhoustay theae for afew days to catch my flight to my home country is my visa is allowed to do that
because it much cheaper to take a round trip flight from guangzhou to hainan than one way trip from hong kong to hainan and one way trip from hainan to guangzhou
if that is not allowed please inform me the best and cheapest plane
thank you