Well, it’s not really a problem, but again, it’s indicative of an iPad being considered a mobile device. As a side note, I’m not sure why you think you need a mobile plugin. Twenty Fourteen is a responsive theme and adapts according to the viewport size. If you were to click the View Full Site link down at the bottom, you’ll see how it looks on mobile devices.
As far as the “problem” goes, I take it you are referring to the extra white space to the side of your images. One solution, as it looks like you’ve discovered, is to float the image so the text flows around it. But in general, yes, if your images were to span across the entire width of the container, you would get rid of that extra white space. Another option is instead of setting a set pixel width for your images, to set a width using CSS of 100% so they will fill the width of the container, and then re-size automatically according to the container width.