The use of handheld computers as a tool to enrich the museum experience has found its way into many museums, opening up new possibilities to increase the attractiveness of museum visits, especially for youngsters. We developed a mobile guide framework that supports the creation of mobile guides and adheres to social-constructivist principles of learning. The mobile museum game we created with this framework aims at developing the social, cognitive and technical skills of the users. Large scale evaluations show the potential power of our approach to stimulate interaction between youngsters and to create a playful learning experience.