The expansion of the Internet of Things (IoT) into diverse sectors such as smart cities, agriculture, and industrial applications highlights the increasing relevance of device mobility. Yet, mobility introduces complexities like packet loss, latency, and energy demands, compounded by the absence of a unified mobility management standard for key IoT protocols like MQTT and CoAP. Addressing these challenges, this paper proposes a Model-driven Development (MDD) approach to abstract and simplify IoT system design, emphasizing pre-deployment simulations to uncover design flaws. Introducing a Domain-Specific Language (DSL) within the SimulateIoT framework, the approach focuses on designing, generating code, and simulating IoT systems with an emphasis on mobility, particularly for MQTT. This includes mobile and stationary devices, alongside fog and cloud integration. A case study on a drone-based forest fire detection system exemplifies the practical benefits, showcasing how MDD and simulation can streamline development and mitigate complexities in IoT mobility management.