A singer in a world of vampires and such? Hehe that sounds like a good second job
(after fighting evil).
If I could give you an advice though, it would be the "be careful with the mystical forces" because when you include them in a long story and are not 100% sure what they're up to, you tend to give them lot more place than what they should have, and they might look like they have no particular reason to be around.
My second advice would be: If you want your story to really have a heart, you gotta figure out it's meaning to yourself first. What's the message you want to tell? Does it come from something you've lived through? Is your main character a representation of you at some point in your life (or something you would've wanted to be?). Cuz all that will change the way you write the story, and even if it might give some depth to the feelings you will show, sometimes if it's related to personal experiences, you can lose sight of the story's main goal.
Another question to ask yourself if you're gonna use the demon fighting thing: don't forget to tell how it originated. Was it always there, in a constant fight with the good forces? Or did it just appear out of nowhere to wreak havoc? And I wouldn't call your group the chosen ones. Special powers are cool, but so much overrated. And it's a lot cooler when a bunch of ordinary kids beat the bad guy with just their wits and perseverance than with the help of the flying fireball attack, or the megazordz (ah power rangers memories
).
I don't mean to write your story, I'm just giving my personal opinion and the advices I think will help you.
Oh, and don't worry too much about what's cliche or not. A touch of cheesy can have a good effect too
Just go with what you want to make your story out of, and if you really have good ideas the cliche shouldn't show up too much