If you have Java development skills then GWT is a no-brainer: it's a gift in terms of client-side web development for Java developers. I'd recommend going for GWT itself rather than a GWT wrapper on another client-side framework. GWT seems to be the 'thinnest' wrapper that offers the smallest client-side download. Some of them do get very large. Plus, you're also operating 'close-to-the-metal', which can offer eased maintenance/configuration.
There are several GWT charting libraries available - so you can choose whether to use Google charts or use another open source library.