I would imagine that taking care of one's children does not require constant interaction. If that is the case then one could WFH for 8 hours a day but space out their time so that they can attend to their children's needs as they arise.
Depends very much on the age of the children. A friend has three, 6-10 years. It is not so easy to work from home when they are five or less. Try with someone else's kids and you will see.