If it was me I would be less offended by the first post -- because it may be that they meant their Facebook post about the emergency to be the way they communicated most effectively, and at their first chance, with everyone about it. They were perhaps very understandably wrapped up in the moment about sorting out how they could best support their child in that situation, to have thought to have made a call to you, previous to making the post to let everyone know. Not saying it was right, wrong, the best thing or not, but they were in crisis at the time and surely doing their best.

But about something like about leaving you out of a celebration at which you would have liked to have been in attendance, I think let them know that, but coming from a place of anger might not be the best approach towards resolving it.

Just my opinion.