How can fallen interact with vampires?

I will be running a Demon The Fallen game where the players will be facing off against an earthbound with infernalist vampire servants. So I am semi expecting my players to seek out local vampires to gather information but I am afraid a simple auspex on the vampire side will reveal the true nature of PC’s and from what I know Camarilla isn’t exactly fond of demons.

My question is how can my players interact with vampires without being ousted and possibly losing their mortal hosts?