Yes, it is safe to give RestoraLax to your 2-year-old daughter if she is experiencing hard and painful stools. The recommended dose for children is 1g per Kg of body weight. You can mix the powder with 100mL of liquid and give it to her once a day. If her symptoms persist, it is important to consult with her pediatrician. Additionally, you can help with constipation by incorporating fiber-rich foods into her diet, increasing her fluid intake, maintaining a regular bathroom schedule, and not ignoring the urge to defecate.