Originally Posted by jiejie

Given the size of the party and the younger demographic, I'd set up something that is more balanced and not so city- and history-heavy. I would lose Xi'an and Nanjing, for starters, though not for the weather reasons moondog mentions. Xi'an is just too far of a geographic outlier and the younger set tends to find it less than fascinating. Nanjing is likewise a bit too history heavy. Instead, I'd get something small town and something active in there. My recommendation would be:
4th-6th Arrival and 2 days in Shanghai.
7th Morning get a van to take you and your stuff to Hangzhou. On the way, spend a half-day including lunch at water town either Wuzhen or Xitang. Mid-afternoon get to Hangzhou for overnight. Maybe see the Impressions West Lake show.
8th Hangzhou/West Lake in morning. Afternoon get van to Huangshan City (= Tunxi), can see the small old town there and overnight.
9th-10th. One day for trip to Mt. Huangshan, cable car up, hiking around, return to Huangshan City late afternoon. Second day for daytrip to the Yixian villages--I'd suggest Hongcun in the morning, Mukeng (requires hiking through cool bamboo forest) in midday), and Xidi in the afternoon, return to Huangshan City for overnight.
11th Getting to Beijing. Moving this many people is probably a job for the train. I'd get a van to take you to railhead at Nanjing South station (this will be about 4 hours by road) in the morning then catch one of the bullet trains leaving around 13:00. You'll be in Beijing by end of afternoon.
12-departure. Beijing. You need to allot 4 full days to this + your departure day.