Yes, Lax-A-Day can be given to a 2-year-old child to treat constipation. It is an effective and safe solution for both children and adults experiencing constipation. The amount of powder to be diluted in a small amount of liquid will vary based on the child's weight. It is important to ensure the child stays hydrated and encourage them to increase their fiber intake, especially through fruits and vegetables. If you have any further questions, feel free to ask.