Visit Xiamen for 3 days

Hi, I am canadian passport holder and would like to see my relative in Xiamen, the problem is I don't have time to apply the visa now. If I flight there for 3 days( round trip from Vietnam). would the free 72 hours transit policy apply to my situation? and how i will do? Tell travel agency when buying tickets? Or is it possible to get a VOA at Xiamen Airport?
Thanks