Oblaaspop
If my family are held hostage in the scenario you describe, I expect they will be murdered as soon as I leave for work. That would give the terrorists the best chance of avoiding capture. I have already decided that, should this happen, I'll contact the police at the first opportunity. I have also decided that I won't pay for my family to have a slight chance of survival with the lives of fifty other families.
Would it not be far less trouble to let the terrorist get a job in the catering company, if they haven’t already?
The hostage method is risky and needs lots of people, planning and coordination. It’s rather different to a bank robbery.