It is part of the coach’s job to guide you along in this process of being a captain’s parent. They should meet with you about 6 months prior to the season to discuss and decide what jobs would be most helpful to them.
You should find out “needs” and/or “wants” regarding additional coaching staff, equipment etc. that fall outside the budget set by the school – plan team budget accordingly.
You should have the coaches define what their role will be in communicating etc. with the team parents and what your role will be
You need not be an advocate between other parents and the coach. If you encounter parents who complain to you about something the coach is doing, you should encourage them to talk to the coach.