I'm probably not a great one to comment - I had watched all sorts of films by the time I was that age. Mum was really permissive about that sort of thing. I watched The Lost Boys when it was a new release - so I would have been 9-10. My kids have also watched some movies that others would baulk at, but I think they are able to process it so I let them watch. If you think that they will be fine with it, then I don't see a problem with letting them watch so long as you watch it with them. TBH, I don't think there would be anything in that movie that would be any more graphic than anything they would have watched in Harry Potter. And great choice of movie too. Much better to 'blood' them with The Lost Boys than with Twilight LOL.