Any question answered...

I think realism is definitely an important factor. Which leaves me with the following:

• Axure (never used but willing to give it a go)
  
• Flash (never used but willing to give it a go)
  
• PHP CodeIgnitor & JQuery
  
• Raw Ruby + SQL & HTML / CSS
  
  

With my novice understanding, if there is a script for how the presentation is going to go, would it be too obvious to make several HTML pages with a 'refresh' button, which is actually a link to a similar looking pages but with different stats (and faking that is it connected to the system)?

Yes - exactly. As long as everyone involved is clear that you a producing a mock-up, and that a mock up is suitable for the purposes of the demo that's pretty much what I would suggest.

Axure is good for that kind of thing but you can also do it in Powerpoint (export presso as web pages)