No one can see Harry underneath the Invisibility Cloak, and Homenum revelio does not work either, as is befitting of a Deathly Hallows item. Also, in my story, Dumbledore was a shade more helpful before his death than in the books. This version of the trio has been previously informed that Nagini is a horcrux. They are also aware that Harry has a piece of Voldemort's soul within him, and that he must let the piece die before Voldemort can be finitely destroyed. Finally, Snape got what he dearly wished and died without anyone knowing of his deep, dark ability to love.