US Citizen flying to Shanghai Sept 11th for Cruise

So I am flying from US to Shanghai on Sept 11th, Cruise leaves for Japan Sept 15th and return to Shanghai on Sept 23rd. Leave that evening of the 23rd to Vietnam for 1 week. Do i need a Visa for China or can i apply for the 144 hour twov? Just want to make sure before we leave, my travel agent said i could use the 144 hour twov!
Thanks!