HBG2 that does makes sense to me. The line in the song "restless bones etherialize" could be directed to our poor coffin guy. Restlessly trying to get out when finally he can and then becomes an etherialized happy haunt to celebrate his wake.
And Smelly, I believe MG13's pun is describing that when your dead you won't see another morning. So no mourning = don't cry over me and no morning = I am dead so I won't see another morning.
No mourning please at his request. (I think it's funny, I never thought about it before.)