Augmented Reality begins to be widely mainstream among children, due to some interactive successes in video games and social networks. Based on this interest, we present CartonEd, an open and complete toolkit suitable for children dedicated to the construction of an augmented reality headset device. The toolkit let the children play and explore augmented reality with and beyond handheld devices. Inspired by the Do-It-Yourself movement, the toolkit includes different components such as blueprints, tutorials, videos, mobile apps, a software development kit and an official website. Among the mobile applications, one is implemented to guide the children through the construction process while experiencing augmented reality. To validate our solution (in particular the construction process and the guiding app) and understand its effect on children in regard to their relation to the augmented reality, we conducted four construction sessions. Our study examines the usability of the guiding app and the construction process. We report in this paper the main components of the CartonEd toolkit and the results of an evaluation among 57 children and teenagers (ages 8-16), showing a positive outcome about their own constructed device (all functional), their feelings and wishes regarding the augmented reality.