Help! Adding multimedia presentation to website

Hi,

I am a freelance web/graphic designer with a client who essentially wants to add a presentation into a website, and I need some advice from you gurus about the best way/technologies to accomplish this.

They want the presentation to:
- Include voice-over narration
- Include supplemental text and images to support the narration
- Include interactive elements such as timelines, where the user can scroll and reveal/hide content.
- Include 'talking head' (or other) videos
- Be editable by themselves on PC (add or change content.. mainly text I think)
- Fit into quite a small content area in their website's template (I'm thinking the only way this will work is to provide links that will open the presentation full screen. There's simply not enough real estate on their site's template to display an effective presentation - make sense?)

They seem geared towards using all Flash and avoiding PowerPoint - yet they freely admit to knowing little about these technologies. I think they largely just want it to look 'cool', have interactivity, and not look like a typical lousy PP presentation with plain bullet points, etc.

However, I have to think that if they want to be able to edit content themselves, then the all-Flash route is a no-go (other than editing basic linked text files to make minor text edits). In that case I would possibly suggest PP 2008; but still incorporating uneditable, interactive Flash animations along with editable content (yet I haven't worked with PP in this capacity - so I don't know how well it works with incorporating sound/video/Flash for the web.)

So... any ideas of what technologies would be best to serve up a presentation like this on a website? Powerpoint w/Flash? All Flash - and just tell them that it's not editable at their end? Something else?

Thanks in advance for the help!