Robotic wheeled rovers have been successfully controlled by activity execution systems that use plans with temporal flexibility to adapt to disturbances. These systems abstract away the detailed dynamic constraints of the controlled device. To control dynamic, devices, such as agile bipeds, we extend this execution paradigm to incorporate detailed dynamic constraints. Building upon prior work on dispatchable plan execution, we introduce a novel approach to flexible plan execution that achieves robustness by exploiting spatial as well as temporal plan flexibility. To accomplish this, we first transform the high-dimensional system into a set of low dimensional, weakly-coupled systems. Second, to coordinate these systems, we compile a plan into a flow tube description, representing all legal trajectories and their temporal coordination. Finally, the problem of runtime plan dispatching is reduced to maintaining state trajectories in their associated flow tubes. The approach is validated using a high fidelity biped simulation.