Keep a close watch on anything MOOC-- I have been pretty underwhelmed by those, myself. It's not that they are not good, because they could be... it's just that it's such a mixture of levels of students and the message board postings associated are often a really messy aggregation of off-topic, rudimentary (to the point of generating face-palm moments), etc. WAY WAY 'biased' postings abound, and often the "moderation" there is minimal if it is done at all.
Great Courses has some interesting things, but I've found that with great materials like that, it's still necessary for my DD to have a discussion component. If I have wished for one thing over and over again throughout the years, it's that she would have an 'adult' suit to crawl into, and an intellectual group of individuals to hang out with and discuss literature and the humanities with-- she eventually gets frustrated with even me on this score. While I'm a polymath and a person with passionate interest in history and literature, I'm simply not an expert in those areas the way that I am in the sciences.
I think that much depends on learning style there-- but the problem with the social sciences is that it is very difficult to generate novel/deep understanding and analysis without a variety of perspectives feeding into your thinking about the subject. With contemporary events, of course, that's easy enough to gain-- but with historical ones, it requires learning to evaluate sources for bias, and being able to ferret out dissenting viewpoints (and not so easy to do in some areas of world history where 'revisionism' has followed events).
I think you're on the right track in thinking of the Coursera, etc. as a supplement alongside a college textbook. That's the kind of strategy that we've used most successfully with our DD.
One word of warning, though-- HG+ kiddos can eventually outstrip that level pretty rapidly. It's only taken DD14 about 2 years to get to a point where she's chafing at that lower-level undergraduate delivery level, and then it gets a LOT harder for a non-expert to help with continued learning/resources.
I sure wish that my dad (a genuine Shakespeare scholar) were still alive to help her.
