Vala is probably the easiest way to work with Gtk+ anyway, so might as well be Vala if the stack is Gtk. I don't know Vala well, but wouldn't mind jumping in with it, scares me a lot less than Gtk in C.
Be that as it may, it was a mistake to roll a different language for this in the first place. It's not really useful for anything else, so unless you're totally dying to contribute to GNOME (very few people do), there's no reason whatsoever to learn it.