For trips abroad where no passport is required, children under 12 must be in possession of a Kids ID. This electronic identity card has to be requested at the municipal authority on time, since the delivery period is usually 3 weeks. For travel to countries that do require a passport, all children under 12 need to have an international passport on their own. This passport is valid for 5 years. The child must be present at the application.
Up-to-date information on the Kids ID and passport can be found here.