Tourist visa for US passport holders going to Hongkong, Beijing then to Shanghai.

My family and I are traveling to Asia end of May, starting in Manila, then Bangkok, Hongkong, Beijing, Shanghai then back to Manila before we come back home to US. I was planning to book my Asia airfares and hotels when we get to Manila. Can we get our China vis at a China Embassy in Manila once we have our itineraries? Or is it better to get it here in the US? Also how long will it before we get it? Thank you.