In recent years, unmanned aerial vehicles (UAVs) have been utilized as mobile edge computing (MEC) platforms to tackle computing resource limitations and communication coverage issues, particularly in areas without fixed infrastructure. However, the independent operation of UAV providers often leads to imbalanced service loads, inefficient resource usage, and limited coverage. To address these issues, this paper proposes a hierarchical cooperation approach for multiple UAV service providers, optimizing coalition formation and task offloading strategies to enhance overall system utility. We model the collaboration between UAV providers as a coalition formation game (CFG) and the joint order is employed to ensure stable coalitions, thus maximizing system performance. Task offloading and resource allocation within each coalition are formulated as a many-to-one matching problem to optimize resource utilization and computational efficiency. The Shapley value is applied for fair utility distribution, incentivizing UAV providers to maintain cooperation. Extensive experiments demonstrate the effectiveness of our approach, with the joint order improving system utility by 4.76% and 31.58% over traditional selfish and Pareto orders, respectively. Furthermore, the proposed offloading scheme shows significant performance gains of 13.22% and 20.24% compared to the shortest distance and random access algorithms, respectively.