Don’t take for granted that you know how the decision will be made, even if you know the decision makers and have researched the options for the decision. Start by simply asking your decision maker(s) how they will make the decision, and what information they think they will need to make a sound decision.
Regardless of who they are, it is always advisable to communicate with the decision maker well in advance of when the decision is needed, providing the facts, options, impacts and deadline for the decision. It is also a good idea to have a recommendation ready to help advise the decision makers. As the project leader, your advice matters, so be ready with a recommendation for what you think is the best option.