Coming at this as a teacher (with a background in IT) I would suggest making it as student centered as you can. That would mean (unless you can meet with the students before hand) being extremely flexible with the syllabus. So you would ask the students something like:

* what problem they have in life they want to solve * what they think is missing from the current web

From this you can go into decomposing a problem into smaller parts and move into programming those small parts, using the tech that is best (here you teach them how to google for tech needed for certain domains)

Of course, you need to open with a few early wins- eg get them to make a quick static web page, then adapt that web page into a dynamic web page with a poll where they could probably have their fellow students vote on and give feedback to their ideas from the previous questions. But the main thing is for you to find out what they want to do, and show them how it is possible via web tech.

And also, remember this is the world wide web. Maybe figure out how to have people contribute even if they're not in Greece via irc, Skype, handouts etc. You may even get close to one on one tutoring if enough people like your idea.

Awesome idea, and great luck to you!