Hi, planning travel to Beijing + Shanghai 7th - 17th May, is this a good time, any travel tips?

Yes, it is a good time, neither so cold or hot.
The clothes for that time is T-shirts and a coat.
For traveling around, it is suggested to book the hotel and the transportation tickets in advance. A well prepared routes and transportation methods are suggested to have. Besides, a local map is necessary or you can use the google map.