Frankly, one overlooked piece of this argument is the students.
If you have students who are interested in Computer Science/Engineering I would recommend C++ or Java, as the experience they gain will be quite valuable for them in the future.
C++ is a more complex language (but has some advantages), if you have a student who is willing to do the research to learn the in's and out's of memory management, references, pointers, etc. then it is a great opportunity to learn coding at a deeper level.
Java, on the other hand, can take away alot of the painful hurdles that a new programmer would encounter, making it easier to get the robot up and running, and makes a better gateway language than C++.
If you have students who are interested in pursuing non-computer related engineering and science, but are still getting stuck with the programming
, then you should consider labview, as it is used much more frequently by non-programming oriented disciplines due to it's graphical nature, and ease of use.
Also take into account your mentors (if you have any that know programming), if you've got a mentor that knows any of the above, then it will take alot of the edge of learning that particular language.