These people should surely recognise that there is no substitute for reducing emissions at source. Its hardly taking all practical steps to reduce carbon emissions if they are flying off to Scotland is it! But that is what the best advice says should be done before considering carbon offsetting, which is what these 'four staff' would probably say they have done with their emissions from the flight.
Even at the offsetting stage one has to be very careful indeed about the scheme chosen because there are some very dodgy ones out there - you just can't 'magic away' our climate problems by handing over some dosh to a consultancy. If the solution was that easy the problem would have been solved years ago!!