Making two versions of the same game is usually quite counter-productive. What problem are you having with resizing your images?
It can be a bit of a balancing act, but for our projects we generally tend to make images at the highest resolution we can. We have several works in progress, and they all seem to look okay on both PC and mobile devices!
Of course you have to take into account project file size, and memory use (hence the balancing act). We've found that creating images somewhere between the largest and smallest screen sizes available to the end project, usually works quite well.
Anyway good luck, hope that helps :)