You can't sell a group
A guaranteed prescription for failure is to present to a group without having first identified and appealed to the critical perspectives of its members on an individual basis.
Source: Sales trainer/consultant Jeff Thull
By the time you present the solution, there should be no surprises to anyone. Everyone should be aware of how the proposed solution will impact them, and enough support should exist to guarantee that the group decision will be a mere formality prior to implementation of the solution.