Thanks for clarifying he's not a foster child. I think one of best tools for parents is having a good routine - set meal and snack times and organized play time. This will be a challenge because you have varied ages. Explain to the 3 yr about the reward system and where he should go when he's mad - tell him when he's mad to sit in a chair until he's calm. If he goes the whole day with no tantrum he gets a star on the calendar. Maybe tell him in the morning enthusiastically - "today you're not going to get mad and we're having a good day" -high five each other. When he's doing something good praise him. I agree it's hard when the problems of one child take away from the others. Best of luck.