The best and quick way to get a Kid’s Portrait is to go straight up to a little one while they are sitting and playing and stand above them and simply call out their name…”Hey Jimmy look I got a sausage roll”.
You need to be ready and have yourself prepared with your right camera setting which I recommend a sports setting so you can shoot the pic fast and take several shots with the motor drive so that your portraits are captured in those few seconds.
Kids move quickly at times and if you are on the ball then the good engaging images shall come your way.