In beijing, you are suggested to visit Badaling Great Wall for easy transportation since your time is limited in beijing, and besides, you can hire a rickshaw to see the hutongs (alley) in beijing, and eat snacks in Wangfujing food street in the evening. There are so many delicious and local food that you may be interested. In Hong Kong, visit Ocean Park and Victoria Peak, and enjoy the harbor view. The nightview of Hongkong is beautiful, quite worth seeing. Good trip!