Language for teaching basic programming
You should perhaps look into Racket (formally known as Scheme, a derivation of Lisp). It's the language taught to first year CS students at my University. Since it's a functional programming language, the syntax and concepts are quite simple compared to C/C++, there are several libraries that can do some basic drawing or networking related things, and Dr. Racket as several debugging features... including a Stepper (i.e it will show and perform one substitution at a time when you click the "next" button). I think that it may be worth looking into: http://racket-lang.org/. It has several other features that you may like, such as teaching modules (beginner, intermediate, advanced, full student levels) and pretty good documentation and examples. The book: How To Design Program (http://www.htdp.org) is a great teaching reference for this language which has a few nice examples using some of the libraries I mentioned above.