Delivery of rail tickets on arrival at Shanghai Pudong airport

We will be arriving at Pudong Friday, Oct. 11 at 14:05, and must get to Nanjing. We had planned to get the train G7142 at 17:18 at Hongqiao station. How can I get the (2) tickets? Where would I pick them up? Does this allow enough time, or should we get a later train? Is there a better way to get to Nanjing?