As a participant and director of LARPing in the past, I must say, that this is awful. There should be other ways that are in-character to gather people, like, a surprise inspection by the Galactic Spacecruiser Authority, or the appearance of a possibly hostile ship nearby (which turns out to be friendly, but, since everyone is here -- story element ensues!). Then, during the safety spiel, you tell participants that all such alerts are import story elements not to be missed if they want to get the most out of the cruise.