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> I'd concentrate first on building internally consistent mental models.

I strongly agree -- and the Lisp/REPL combination is extremely helpful. Specifically, I believe a Scheme-based approach is the best way to learn programming, even if you eventually decide to migrate to something less fortunate like Javascript or Python ... in under an hour from your first exposure you can be thinking about stuff rather than the syntax of loops. I won't attempt to justify the pedagogical reasons for this choice here.

Specifically, I'd recommend (1) using Racket, a "batteries-included" Scheme derivative with a simple IDE/debugger, and either (2) Concrete Abstractions (free at https://gustavus.edu/+max/concrete-abstractions-annotated-to...), or (3) the upcoming book Realm of Racket (coming in May), which will cover some of the same CS 101 material as well as GUI and distributed programming via writing games in Racket. (There is an earlier book called Land of Lisp but I feel its environment (CLISP) and coding practices are rather baroque.)

Depending on your student's interests you could simultaneously look at some web programming (plenty of HTML/CSS material is available from Mozilla, Google, etc.; there's an upcoming Udacity course on HTML5 game programming), lower-level stuff like assembly, arduino, or whatever.

Hope this helps.