I would recommend Java for this kind of situation.
Java Web Start is a great technology for deployment and fairly easy to set up. It makes your deployment pretty painless and automated from your perspective: all you need to do is maintain a web server with the right .jar files and appropriate JNLP descriptor (a short XML file).
From the user's perspective it is pretty much as simple as "click on web link to run app" (you might also get a click-through security notice depending on OS / browser / security setup but most users can handle these :-) ).
A big advantage of Java is bytecode portability which means that you don't need to recompile for different platforms if you stick to pure Java / Swing. This is massive advantage for deployment if you are deploying to a heterogeneous set of platforms (e.g. several versions of Mac + Windows + Linux)
Java clearly requires the user to have a JRE (or be willing to install one) but this problem is overstated - most users already have a JRE nowadays, and Java Web Start includes the ability to install a JRE on demand in modern browsers. Furthermore, the users who both don't have and can't obtain a JRE are either a) on ancient technology anyway and unlikely to be your customrs or b) in a heavily locked-down environment where you probably won't be allowed to download and run native C++ Qt code either.