Whatever reason was given, I would not allow a passenger to be inconvenienced by another.
About time people take responsibilty for their own children.
A few years ago, one of my colleagues allowed a passenger to occupy the jumpseat instead of having to wait for the next flight.
Then the company received a complaint from said pax to the effect that the service wasn't good enough and it was uncomfortable. Seemed to have forgotten that the crew were doing HIM a favour.