This is one of the occasions where I would start panicing. If you have babies and mould caused by condensation, you need to ventilate. Your house is about the same age as ours, but for the old part at least, we still have most of the original leaky wooden windows. We don't have damp problems.
There is a conflict between the modern requirement for heating and reducing heat losses cos J. Pres**** says so, and the age old need for biological systems (like people) to have fresh air. I choose fresh air. Humidifiers will not give satisfactory performance in a house, unless you seal it up, and stop generating excessive moisture. (This is easily done by stopping washing with hot water, no more cooking and definitely no breathing) The most efficient way to lower humitity is to shove the damp air up the chimney and give it a helping hand with a fire, (wood burning stoves work well).
Because of todays building regulations, we have to install sealed window frames, then they have to put a ventilator in them, which people keep shut. If you have a leaky frame and put a jumper on, you will be reasonably and a lot more comfortable.
On a serious note I would do something immediately about the mould growth, for both you and especially your babies. Washing the surfaces with fungicide is not the cure, you need ventilation. Ventilation doesn't make you ill, mould spores do.