Question about free 72 hour Visa

Hello - Me and my family will arrive in Hong Kong on 25 June 2016 in the evening. (6.00pm)
On 26 June we fly to Guangzhou with Dragon Air - Arrive at 9.25pm
On 29 June we depart and fly to Hanoi in Vietnam. Departs around 4.20pm with Vietnam Airlines.
Do we qualify for 72 hour free Visa - Thanks in advance.