In this paper, a planning method is developed using convex optimization for concurrent station keeping and momentum unloading maneuvers of geostationary satellites equipped with on-off electric thrusters. Prediction models for coupled orbital and attitude dynamics are used for generating concurrent maneuver plans. Since the satellite's attitude dynamics is fast compared to the orbital dynamics, a dual-rate model is proposed for addressing time scale differences of the two coupled systems. Based on such a model, a convex optimization problem is formulated and solved in a receding horizon form, which minimizes the fuel consumption and the number of required maneuvers. The proposed algorithm is verified using numerical simulations, taking into account major perturbations in the geostationary environment. The performance of the proposed method is analyzed in terms of fuel consumption and constraint enforcement.