The number one thing I can say about this is to tread carefully. Anne Rice is notorious for disliking fanfic/rpgs and such based on her works. You might consider keeping it friends-locked or ambiguous, if you do choose to pursue it.
Another choice it to make it partly original, inspired by Anne's world, but then it'd have to be OCs only so there's no room for confusion. That said, I have seen a few games around in the fandom, so there should be interest to garner. Good luck!