If your group is most familiar with Java and you're planning on doing significant amounts of client-side functionality then you should at least evaluate GWT. The type safety, Eclipse debugging and shared code between the server-side/client-side will feel comfortable to your Java development team.
However, if your team is used to JavaScript programming with jQuery or another JavaScript library then it may be easier to stick to a technology that is pure JavaScript. GWT has a way of taking over large sections of the page, which is unfamiliar to most JavaScript developers. By take over the page I mean that typical GWT code likes to create its own DOM Elements instead of adding functionality to existing Elements on the page. This is why many GWT apps have a "loading..." screen when the page first loads. This isn't necessary, but it's the most common style of GWT development.
The fact that generated code comes out of GWT is less relevant for most GWT developers. GWT allows you to compile Java into something equivalent a normal java *.class file but in a JavaScript syntax that the web browser understands how to interpret. GWT acts much more like a compiler than a template-driven code generator. There are times that you will need to inspect the generated code but for the most part your debugging will be in Java via your Java debugger.
Another thing to think about is that regardless of the client-side technology you choose, your development team will need to be familiar with HTML, JavaScript, CSS and browser programming in general. GWT lets you write client-side code in a familiar Java environment but it doesn't hide the fact that you're working from within a browser.
