VB is more distant from other languages than Python, more limited in its direct utility, and less useful for teaching general CS concepts.
Python and JS may not be the perfect set of choices, but they are good set, and certainly either is far better than VB.
Also, Processing in particular is a very smart option. I know that when I was learning to code, being able to draw cool patterns and stuff on the screen was really motivating.
Javascript for teaching programming to children is an awful idea, though.
That it naturally runs in a browser is an awful reason to use it. Use something that compiles to javascript if you feel web programming is so important.
VB is a bit old and outdated at this point, I think.
(btw, my handle is not related to this site)