The stability and power sharing properties of droop-controlled inverter-based microgrids are adversely affected by model uncertainty, and inverter parameter drifts. Even when frequency stability may be guaranteed, power sharing remains sensitive to clock/frequency drifts. A novel coordinating control law is proposed to overcome these issues. It guarantees both stability and power sharing in the presence of parameter uncertainty, including frequency drift. The new control law uses sparse inter-node communications. Conditions to achieve (local) stability with power sharing are presented. It is also shown that our power sharing control is robust to reasonable clock drifts and very small droop coefficients. Simulation and experimental results illustrate the performance of the proposed control law under clock drift scenarios.