Haha oh dear. They are Aer Lingus' aircraft (well Air Contractor's but you know what I mean). As such they are perfectly entitled to chop and change as they see fit. Is it annoying? Certainly yes for those planning on flying in or out of Shannon. The French are picking up the tab. I'm told everyone effected in either DUB or SNN has been called and offered money to fly a day or 2 earlier or later, or an alternate booking with UA/DL etc, or a refund.
They were told they would have 2 more A330s next week than they actually will. More pax effected in DUB by cancellations than SNN. Less pax overall negatively effected this way. Also with the week that's in it most U.S. tourists want to be fly to Dublin next week for the parade.