I believe Whitman uses the beauty of love making with a woman (and a man for that matter) as a further way of expressing his joy and appreciation for the human nature and the existance of variety. We see in "Song of Myself" as well as "I sing the body electric" that Whitman is facinated by the ways in which people interract, isolate themselves, fantasize, relate and live. I believe that this entire poem is a combining of souls that all came from Adam and Eve. By calling it "Children of Adam" he ties in the end love scene by showing that humans are close to God in the way that Adam filled Eve and we fill eachother, making new generations of god-loving people and people that bring variety for poets like Whitman.