I made most of my games in Javascript before I realized that my comfortable little IE6 on an optimized XP professional machine was not standard enough or permanent enough to support it.

The biggest problem: audio. Audio support in Javascript is abismal and nothing resembling cross platform.
I always used the embedded media player with IE. Don't do this. It was incredibly convenient under the conditions in which I picked it up, but those conditions were luticrously ideal for exactly that. Your audience will not have those conditions.
Modern Javascript audio? If you can get it to work, please let me know.

However, Javascript worked very well for me in terms of learning loads of useful basics, and some of the things the web browser can be made to do. I would not discourage trying to develop Javascript games; just acknowledge that they're probably going to be mostly text-based.

...

*Considers trying to beat IE whatever-version-we're-on-now into running my games from 2006* *Decides it is not worth the frustration*

C++ is probably overkill.
It depends on what you want the user experience to be. Is there a game window? Is there visible text? Will it use Sapi/screen reader output? Will the player choose from a list, or enter a word in a prompt?

For this sort of thing, I might recommend BGT, but it has very little in terms of visual output (just alert, input_box and question, which are similar to Javascript's alert, prompt and confirm).
Python maybe, but distribution would be troublesome.

BGT is Angelscript, which is in fact object oriented.  javascript is not, technically; it doesn't meet all the checkboxes.
Python distribution is no big deal if you aren't worried about DRM.  CAE, I'm sorry this keeps biting you, and I'm not sure what to say.  Py2exe is easy so long as you're not using zipped eggs and Python 2; the version for Python 3 fixed this problem.  If you do have to use Python 2, Cx_freeze professes to fix it.  Your experience with Python distribution is not typical, though it may be a barrier to new programmers.  I'm not sure what parts of Py2exe you are finding unclear.  It's pretty clear to me.
If you only care about Windows, C# is probably not a bad choice.  I've heard good things about SlimDX, or you could even just use XNA (it's no longer actively developed, but would meet your use case no problem).  C++ isn't exactly overkill, but it is a lot of extra complexity for nothing.

Size is important, but I don't think that important.  2 or 3 meg isn't a big deal.
Everyone in the first world won't have a problem with 2 or 3 megs.  The game is not going to be wildly popular or commercial, as this is academic.  I'm not sure how many sounds are involved here, but having a small executable package may not be a real concern.  As the game grows, the program's size as compared to the size of art resources and level maps and such will shrink; if Swamp were to be rewritten in Python, it's size might maybe grow by half a percent.
There are also ways to shrink the ap, but this is a case-by-case basis.  Even so there's other options that one can use in the first place.  I will say that Pyglet looks like it solves most of the Pygame audio is hard problems and most of the o god here come the keypress if statement problems, however.

python is what you want.
If you only wish to support safari, Firefox and Chrome, use HTML5's audio player and javascript. They work... OK... together. It is nothing like working with python though.
I did try and create a prototype for a game using javascript, html and css, but it was a little ugly.
Python is really the easiest to make distribution packages for, for something like this pyinstaller would make one small .exe file for windows, and I'm not sure, but I think mac and linux can both run the script out of the box.

Only that you won't have any graphics or UI.