I think this is really cool, though the cynical part of me thinks that so will the social media strategists of quite a few celebrities out there, looking to promote things around Christmas...
Bill Gates has been aggressively giving for several years now, and he's quite consistent with his messaging regarding the need to give to and enable the quality of life in the third world. If anything, the strategy is to put a spotlight on those causes, rather than himself.
The fact that your parent poster is apparently unaware of the fact that the work done by Bill and Melinda Gates Foundation had a huge hand in eliminating polio in India would be a good example. The country just marked two years without a new reported case.
There is a lot of unimportant noise out there, and a lot of education and awareness holding needed to keep moving the world towards the better.. everything counts.
If throughout the unwrapping of the gifts, there was a Microsoft Surface, then I'd agree with you but for the most part I believe this reads as genuine.