What can I do to get rid of a feeling that my wife and I have that one of our children is about to die, even though he is not suffering from any illness?

You must reject this feeling and sensation you find in your heart, for it is from the whisperings of Satan. So, fill your heart with the remembrance of Allah and occupy your limbs with His obedience. Do not surrender to these delusions. Through faith, the heart finds tranquility and the servant is safe from fear and anxiety. Allah Almighty says: "Those who have believed and whose hearts are assured by the remembrance of Allah. Unquestionably, by the remembrance of Allah hearts are assured." and "Those who believe and do not mix their belief with injustice - those will have security, and they are [rightly] guided." The distressing mirrors in a dream are from the whisperings of Satan, so repel them by persistently reciting the prescribed adhkar, especially the adhkar before sleep, Ayatul-Kursi, and the morning and evening adhkar, as well as those for entering and exiting, and do not speak about them to anyone. We advise you to fear Allah, maintain His obligatory duties, and stay away from His disobedience.