Children learn from example so maybe if you stop yelling they will, this is where it comes from, they copy ,what are the activities you do with them ,may be good to seperate the activities up to do individually, get Dad involved perhaps he could do a lot of the Physical outside stuff,,what are the dynamics does the older girl start the behavior then the 4 year old gets upset, maybe if you keep the older child busy , seperatly and the 2 year old will do his own thing anyway. Give them individual tasks they will like ,.