Players should probably have a main/movie-canon character, and then a spare/ancillary character, just to have a double.
I'd be more concerned with finding more players first, though! :) Wait for a bit; we don't have to push this forward immediately.
I would like to have Jareth, but if you know of someone who was born to portray him I'd give that up. And of course you can grab Sarah! I imagine you've had lots of practice with her. :)