Here are some examples of reasonable portion sizes for a young child: A mini candy bar, one or two small cookies, or a kid - size ice cream cone. (babycenter.com)
Fill your plate the first time with reasonable portions then eat slowly to give your body time to register that it is full. (wholehealthnutritionvt.com)
Some of them I modified so they are better suited for reasonable portion sizes. (coachcalorie.com)