It is important for children to have a balanced diet in order to receive all the necessary vitamins for a strong immune system. If a child's diet consists of a variety of vegetables, fruits, whole grains, they should be getting enough vitamins through their food. However, during the winter months when exposure to sunlight is limited, a vitamin D supplement may be beneficial to prevent deficiencies. Ultimately, the decision to give your children vitamin supplements should depend on their overall diet and potential vitamin deficiencies.