Students and schools are increasingly equipped with smartphones and tablets. These mobile devices can enhance teaching in many ways. Mobile Learning Games (MLGs) for example, have shown great potential for increasing student's motivation and improving the quality of situated learning. For the past few years, the research community has been working on authoring tools that allow teachers to create and distribute their own MLGs. The development of these authoring tools is challenging and time consuming and even more so if the objective is for these tools to actually be used in classrooms. The Design-Based Research (DBR) paradigm was precisely developed to address these central issues of Technology Enhanced Learning. It involves co-designing and testing with end-users from the beginning of the project. Although DBR increases the acceptance of new educational tools, it also adds several challenges, including the complexity of involving teachers and students in real-world situations and creating several versions of the tools that will be improved iteratively. In this paper, we aim at providing design principles and practical guidance on the way to develop such authoring tools, based on our experience. We conclude on lessons learned from this project and discuss some systematic issues we faced.