I don't see how "graceland" could be just a placeholder word. It is integral to the basic story of the song, which is about a father and and son driving through the Mississippi Delta to see Graceland, which is a popular tourist attraction in Memphis, TN (at the top of the Delta). If it were another word like "wasteland", it wouldn't make sense to the story. As far as any deeper meaning, that's open for interpretation.
I don't see how "graceland" could be just a placeholder word. It is integral to the basic story of the song, which is about a father and and son driving through the Mississippi Delta to see Graceland, which is a popular tourist attraction in Memphis, TN (at the top of the Delta). If it were another word like "wasteland", it wouldn't make sense to the story. As far as any deeper meaning, that's open for interpretation.