The Watch - IDEA

I need some feedback on a story line that I had for my newest novel. It's called 'The Watch', and I came up with the idea when I was sitting in RE last friday. My teacher was talking about the Paley's watch theory, and it just make this idea spark in my head. I have asked some of my friends and family what they think of it, but we all know that they can be a little bias.

The Watch

What if there was a watch that could alter what time era you were in? You could go back in the past, stop things from happening and then change the future and make it a better place for you, right? However, if you change just one thing in the past, it could change everything in the future. This is the story of six teenagers who change something, and then have to decide between the future of the entire world, or their happiness. What would you do?

Okay, so far I only have all of the character's figured out and some sort of story line that they're going to have:

Brayden James Stark: He's a male model that doesn't believe in any of this changing the past crap. He also has a huge crush on Kaylee but their relationship is being stopped by Jolene.

Kaylee Savannah White: She's the sweet Okie girl who just wants to get her father back home. Sure, Brayden's mutterings to himself about how this is all bull gets on her nerves, because she wants to believe that her dad can come back home. She wants to be with Brayden, but Jolene keeps pushing her away from him.

Jolene Helen Golding: She's a bitch and a half. She cheated on Brayden's after catching him looking at a girl in a bikini at the beach, but now wants him back. She's wants to go back into the past and change the thing that she did, so that he'll be hers in the future. She hasn't told anyone this real reason, and just uses a coverstory.

Hunter Lee Banes: He's the gay one. He hasn't found the right guy for him yet, but he's determined to find someone at some point that can keep him happy and satisfied. He wants to change things that have happened in the past to stop the homeless loosing their houses, and the poor having no money. He wants to stop all of this suffering in the world for the people less fortunate than himself.

Samuel Marcus Feilds: He's dead. Unfortunatly, he doesn't know this and neither do the other people in the group. They just think that he's a guy that's pining for his lost love. He's not a ghost, or a zombie, but he looks like a real person, and acts like one. But, in all reality he's dead, and when he brings back Gracelynn, he'll go back to being dead.

Gracelynn Katie Moore: This girl doesn't come into the story until about halfway through when they've gone back in time and changed the thing that went wrong. She comes back alive, but is in a wheelchair and is paralysed from the waist down. She was a passionate dancer and gymnast before she died, and just wants to have that back again. Sam's alive in the future too, and in the same condition as her. However, he's not just paralysed, but had to have his legs amputated. Gracie just wants to go back to being dead when he tells her what they did, as she can't live in a wheelchair for the rest of her life.

...What do we think?