Oh I think R http://www.r-project.org/ would be more suitable for you, because learning C++, esp. Qt isn't easy. R can be learned by everyday business people, so you can surely do that quite fast too.

Qt is an awesome C++ Framework that comes with full-blown IDE (Integrated Development Environment) not just a simple Editor and works across all platforms.

Processing is a Visual Programming Language: you find it here: http://Processing.org and here for the web http://Processingjs.org

You could also use a a dynamic and programmable charting library like D3 http://d3js.org/ but that would be more useable for the Web or a Desktop that Shows a Single page only or your own Browser in Kiosk-Mode (Fullscreen).