plan to visit shanghai on 9 april ,then BJ 11- 14 april..what s your suggestion

During that period of time, the temperature in Shanghai 55 F to 74 F. It's warm and comfortable.
The temperature in BJ is 48 F to 75 F. It's cool but not cold.
So you can bring your jackets, jeans and T-shirts.

These two cities have many popular scenic spots and delicious local snacks.
In BJ, you can go to Tiananmen Square, Forbidden City and Great Wall. Peking Roast Duck is one of the most typical food in this city.
In Shanghai, The Bund & Huangpu River, Nanjing Road , Yuyuan Garden are good choices for you. You can also easily find many snacks outside Yuyuan Garden.
Have fun!