Hanks' son, afraid he's drifting more deeply into a relationship with this other woman, contacts Ryan about meeting his father in New York atop the Empire State Building. He then flies alone to New York. When Hanks' discovers his son is missing, he's frantic. His loss would be devastating, coming so soon after the death of his wife. One purpose of this scene is to allow the audience to experience Hanks panic over his son being missing.
Hanks flies to New York.
Ryan goes to dinner with Pullman. She accepts that hers will be a life of mundane reality. This particular date happens in a restaurant with a view of the Empire State Building in the background. What comes out is that Pullman does not want to marry Ryan if she doesn't love him in that special way she seems to feel for Hanks. There's a reversal of the scene based on Pullman's reaction to events, not Ryan's.