Loose Itinerary Check

I will be taking my first international trip to visit China with my girlfriend and see the sites as well as visit her family. Our trip dates will be 5/14 - 5/29 so 16 days total including travel. The things we have set in stone right now are starting with a 4 day guided trip in Beijing. We need to spend time in her hometown of Ningbo, then visit family in Hangzhou as well, maybe 6 days total. We plan to fly back home out of Shanghai and visit her friend there to finish our trip. We really wanted to add one more city to our list - Chengdu or Chongqing, but in reality I think we are likely tapped out already; just want to get confirmation it would be taking on too much for our timeframe. Cheers