Context: The use of diverse mobile applications among senior users is becoming increasingly widespread. However, many such applications exhibit accessibility issues that negatively affect the user experience for older adults. A primary reason is that software practitioners often lack the time or resources to accommodate the broad spectrum of age-related accessibility and personalisation needs. Current development tools and practices tend to promote one-size-fits-all interfaces, offering limited capacity to address the diversity of senior users’ requirements. This highlights a growing need for approaches that support the systematic creation of adaptive and accessible application experiences. Objective: To investigate a model-driven engineering (MDE) approach that supports the development of adaptive and accessible applications for seniors. Methodology: We introduce AdaptForge, a novel MDE-based approach that enables advanced design-time adaptations of mobile application interfaces and behaviours tailored to the accessibility needs of senior users. AdaptForge employs two domain-specific languages (DSLs): one to define users’ context-of-use parameters, and another to specify conditional accessibility scenarios and associated UI adaptation rules. These rules are interpreted by an MDE workflow that transforms an app’s original source code into personalised application instances. We conducted qualitative evaluations with professional software developers (interviews, n = 18) and senior end-users (three focus groups, n = 22) to assess the feasibility and practical utility of AdaptForge. Findings: All senior focus groups responded positively to the adaptive UI prototypes. Similarly, almost all developers (17/18) emphasised its potential to make designing accessible, personalised apps and their UIs more intuitive and less burdensome. The majority of developer participants expressed that AdaptForge could evolve into a practical/industry-standard development support tool, contingent upon improvements in areas such as code scalability, maintainability, readability, version control, and deployment of adaptive applications.