Most parents should base this decision on first and foremost their daughter's face shape. Many tween girls will have the desire to wear adult sun glasses, but it is best to stick to children sun glasses if their face hasn't caught up to their mind in terms of growing. Many children sun glasses have fun sequins and embellishments, so try to sell your tween daughter on them for that reason. Should she complain that they are too "baby-ish", seek out a pair of simple pink or aqua colored frames. Many tween girls will not complain about a difference between child and adult styles unless they have been informed that their new outfit or accessory is in fact made for children.