I have seen the American cemetry from the air. Looks very impressive with the lines of white crosses. And also seen it on the ground.
I think Manila Ocean Park is a good place to go. I didnt spend much time in Manila even though I stayed in the hotel there. I spent a lot more time in Cavite in Island Cove hotel, water park, "theme park" and zoo.
http://www.islandcovephil.com/about/
http://www.islandcovephil.com/
It is within a taxi ride of central Manila.