According to our experience, 4 days is enough to visit most highlights in Beijing at a relaxing pace. Here are some popular attractions of Beijing and suggested time for tour.
Tian'anmen square, Forbidden City, temple of heaven, Beijing roast duck for dinner (one day).
Mutianyu (a famous section of the Great Wall of China), Summer palace (one day).
Folk culture experience (old alleys in Beijing), visit the local family, learn to make Chinese dumplings for lunch (half of the day)
Hike along the Great Wall of China in Mutianyu (one day).
A walking tour of the Great Wall (Jinshanling and Simatai section) (two days).