If you do a search, you'll find a couple of very detailed threads re sightseeing in Beijing area....having a local guide for certain visits would be helpful. Knowledge of Chinese is absolutely not necessary and you should try to set aside at least 3-5 days. May is still not hot yet and you will have a fab time.

Shanghai is a different matter - as far as sightseeing, it's not even close to Beijing. Unless you're into art, fashion, lots of lights and glitter, etc. And there, unless you speak Shanghai dialect, you'll be treated the same