Frank is shown meeting with Rev. Wakefield and seeing his son Roger. In the first book both Frank and Claire meet Roger and later remembers him when she meets him as an adult in the 1960s.
"Both Sides Now" is the name of a song by Joni Mitchell. The song is about the conflict between seeing the beauty of things on one hand and seeing the artifice of things on the other. There is likely little relevance to the song other than the title.
The date of the story in Frank's reality if December 21, 1945. This was the date of the death of General George S. Patton, as is being reported on the car radio.