Trans-media robots, capable of operating across diverse environments, add significant complexity for multi-robot task allocation and planning problems. This paper introduces a novel approach to plan missions for such multi-robot systems, that addresses the associated specific complexities and constraints. It streamlines the overall mission planning process by decomposing it into tractable sub-problems, and addresses the issues of coalition formation, path planning, and task scheduling. It provides mission plans in very little computation time and allows to tackle large missions intractable by global planners, with negligible loss in plan optimality.