About the widescreen issue, you might want to take a look how the film industry deals with this problem with DVD releases. This link has some pictures and text to describe how they work around it
Understanding Aspect Ratio
I think that you should just go widescreen, if it were a game that would be released anyone playing in 4:3 would have to be letterboxed. While not ideal is the best way to ensure that they don't suffer any problems such as the enemy outside of screen space.
Hope I've been of some help!