You gotta give the PCs a chance to rescue the hostages. But, you also gotta give the PCs a chance to fail. You don't need to make it like the first Rainbow Six game where if you make even a little bit of noise all you hear is "hostage down, hostage down, hostage down, hostage down". But, if they go with a dynamic entry and end up flubbing the surprise round, well... guess you got some 'splainin' to do.