It was good to finally have an out of the blue event , especially during Australian hours for once, normally Calypso events happen when we are sleeping (2-4am in the morning), and also loots and rare items drop during those times.
Problem with announcing an event before the VU comes with risks, for one alot of people have issues when downloading the VU. And maybe certain spawns may have not ben turned on.
But yes im in full agreement with your second option, announce an event for a certain day and time, and only when the time comes post whats needed to win the event, so people are prepared when the time comes.
Even though it took a while to spawn that Skreel, had to kill like 20-30 mobs before he showed up and each mob is 2000HP, but it was a challenge , even to kill it.