From a German point of view, it's not excluded to put families in detention, but as our colleague from the commission said, as far as the EU return directive—which is important in this situation—is concerned, there has to be very strong scrutiny of the principle of proportionality, so you would put a family in detention in a very special case.
Evidence of meeting #40 for Citizenship and Immigration in the 41st Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was c-31.
A recording is available from Parliament.