Family New Years visit in northern Shanghai and world like to revisit the Terra-cotta Soldiers.

Claudia, taking high speed train for the return trip is the quickest way.
You can take an early high speed train from Shanghai Hongqiao Railway Station to Xian North Railway Station in around 7h, and you will find tourists dispatch center when you get out of the train station. You can buy the entrance ticket of the terracotta soldiers site there and then take a free shuttle bus to the site.
Stay one night in downtown area and get back to Shanghai on the second day.