The person caring for the children needs rest that does not require first arranging everyone’s comfort.

Rest that has to be organized first is not really rest. If the break only starts once the meals are made, the clothes are out and every eventuality is covered, then the work was moved earlier rather than lifted, and the person doing it has not actually stopped at any point.

Take the whole thing rather than a few hours of it: the decisions, the meals, whatever goes wrong while you are in charge. Say when you will hand it back, and do not ask where anything is kept.