For successful practical collaboration/cooperation/coordination for the lifecycle of an aid effort, you’ll need a well-considered overall structure that addresses all aspects of the planned and anticipated interaction. It would need to define who the stakeholders/partners are and how they will interact — which means defining an acceptable process for someone to lead the coordination without implying that they are leading the aid effort itself. It will also need to reflect the reality of the situation and clearly capture the roles and responsibilities of all involved for this effort specifically, being careful to acknowledge that this agreement doesn’t compromise any partner’s independence outside the defined scope of the agreement. It should also help each partner present the cooperation in a positive light to their respective constituencies — the moral high ground being the focus on the needs of the mission (while maintaining the integrity of each organization involved).
Actions mean so much more than words, and demonstrated willingness to forego total control for a greater result (and the prospect of follow-on collaborations) is a powerful selling point. Plus, the next time, it should be easier/faster to put such an agreement in place.