What do you need planned. There are plenty of people who can help, from flights to routing, to things to see etc. May is a fine time. It will be hot, humid and stuff, but that means more lovely Shanghainese women wearing less clothing

In other words if you have the finances (which can be cheap save for the flight, then by all means go. Look into some guidebooks to give you ideas. Then do a forum search and ask whatever you want...