What Could Be The Underlying Cause Of Mood Swings, Irritation And Tiredness In A Child?

Hi, my son, 8, has been complaining of feeling sick on and off for about 4 days now and we have both been constantly tired for the past week despite getting plenty of sleep. He does look washed out at times and flushed at others. Both our moods have been out of sorts too, both being irritable and him misbehaving a bit. There are two family friends whose children have also been complaining of feeling sick and have been tired and sleeping lots for weeks now, one of them for over a month. And the mother of that little girl has been unusually tired for even longer. Is there some sort of virus that could be underlying? My sons tongue also has a white film over back half with red dots.