Ds1 just turned 3 last month, much of the time he is a lovely affectionate little boy, really polite and kind but at time I find his behaviour so hard to deal with. So for example today we were in the bank, he was playing nicely with the toys put out and when I said we needed to go he came no problem. When we got a little bit down the street he started suddenly complaining dragging his heels that he wanted to play with the toys. I bent down to explain that he could play with the toys at the doctors (not in an angry way) and he slapped me across the face to knock my glasses off. This is something he does quite often, he will laugh hysterically afterward even if I'm I telling him off.
Because of what he did I said no TV for the rest of the day, which he did seem sad about. When we go out I know if he's not distracted constantly he will find something destructive to do i.e. kicking when in the trolley, pulling off his baby brother's hat and throwing it as far as possible, running off and throwing himself on the floor, pulling things off shelves. He goes to preschool five morning a week and they never have any problem with him, it seem he only acts aggressively to me, sometimes his brother and occasional dh. When he goes to visit his grandparents all bets are off, he becomes an absolute nightmare (I know this is because they excuse a lot of his behaviour) but it's got to the point where I dread taking him over there.
Any advice/tips on how to manage his behaviour would be greatly appreciated. I've lost my temper in the past and shouted, which just makes the situation 100x worse so would love to hear anything that worked on your little ones at that age.