As seems to be clear any discussion that is lead by technology and implementation rather than a problem is going to flounder.
I think we should first focus on a subject area - and then try to find a target audience age or skills level (for example beginner etc).
Once we have both of these we can then look at the kind of problems that people face in that area at that age - this may in turn make us review the choice of subject as others may be more or less challenging. In turn we will probably review the age range of teh audience and the experience we are trying to tackle.
Once we have that then we should look to take what we have learned and the solution to that problem and see if it is more broadly applicable.
Here are a list of subjects to start us off (I'm British though and you may other names for them in the US).
- Religious studies
- Information Technology
- Community Studies