mysterious fog/smoke research

In this trailer there are a few shots of actors in smoke, this makes it alot more mysterious. We have decided that this is a good idea, and will save us buying extra costumes and eye contacts as you wont be able to see the actor.
From this we had an idea of a little girl on a road with mysterious smoke/fog, and whilst this is happening to let the child sing a nusery rhyme, and then in the rest of the film mabey the sound track of that song. We thought we could get a girl or boy from one of the years (most likely year 7) to do this. We like the idea of an abandoned playground as it gives us that horrific feeling, of a playground being haunted or alone - which shows that its the end of the world mabey? We also like the slow and short noises in the backround that remind us of the zombies shouting , which usually makes the watcher scared more.