Ni hao! Traveling to Hangzhou for 1 day with my family, Witch is the most recommended things?

Im in China and my family is coming to visit me next month. We flight from Zhangjiajie to HZ, we arrive in the night and we have whole next day to visit the city, then we take a late train to Shanghai. My parent are in the 50's, most recommended places to visit and fastest way to do it? Thanks a lot