Kirigami, the art of paper cutting, has offered a versatile way of constructing a reconfigurable structure from a 2D planar configuration into a target 3D shape. While several strategies for its design have been reported, little attention has been paid to the mechanical properties when deployed. Here, we investigate how to control the stiffness of bistable kirigami surfaces in the deployed configuration while maintaining the target 3D shape. We develop a computational procedure that can be used to design various bistable kirigami surfaces. Their deployed 3D shape and stability as well as the nonlinear stiffness can be successfully predicted as validated with experiments. Using the proposed approach, we found that the range of stiffness for deployed bistable kirigami surfaces can be significantly broadened by using spatially varying hinges without altering the shape and stability of deployed structures. We expect our study would advance the design of reconfigurable structures having identical shapes but different mechanical properties.