Unfortunately what you're doing is going to take a lot of effort / very difficult to do if you're just starting off. When designing for both web and mobile it's best to start off thinking about both in mind. There isn't a better program than Dreamweaver for what you're doing, however you might want to check out something called Zurb's Foundation.
Zurb's Foundation which you can find here
. It will automatically scale images and boxes to fit to mobile devices once the resolution crosses a certain reduced size. It's extremely handy for what you're attempting to do and I highly suggest taking a look at it.
Best of Luck