The thing is, if you're using Python you don't implement lists, you use the built-in functions. So it seriously depends on what you want to teach.
If you want to teach data structures, C is a better language, because you aren't teaching them to ignore the characteristics of the language. If you just want to teach basic sequencing, etc., something like Scratch is better. It's sort of a graphical subset of Smalltalk adapted for simple animations, or perhaps a cross between Smalltalk and Logo, but the programming is visual rather than typing. It's designed to be useful for grade school children. It's great for teaching sequencing, composition, logic, etc. It's lousy for teaching data structures.
Personally, I can't see any justification for selecting VB *or* VB.net. I.e., I can't imagine what you are trying to teach that would make VB the preferred language. And while Python is a better choice, I can't see that as an introductory language either. Were I doing it I'd probably have them use Scratch first and then switch over to C, or a C++ subset that was equivalent. This would, however, be a jarring transition. Scratch is a contained environment designed to be attractive to young children. It would be an easier transition if one started with Squeak's etoys, but it would make for a rough start, and the last time I tried it (years ago) there were several bugs that would make getting started difficult.