Apologies, but this is a sore spot for me. First, it's relevant to remember that we are NOT dealing with Collegiate or Professional players, or games. Our clients are High School Interscholastic athletes. Our job is to assist those responsible for making decisions that they correctly understand their options.
Although it's both common practice and beneficial for Coaches to ALSO understand complicated or unusual penalty options NF 2-32-5 CLEARLY advises, "A Captain of a team is a player designated to represent his team during: (a) The pregame and OT coin toss.
(b) Penalty decisions following a foul.
(c) Ball placement on a try, kickoff, after a safety, after a FC or awarded FC, a Touchback
and to start an OT.
At higher levels it is common place to direct these decisions EXCLUSIVELY to coaches, however at the HS level (and below) developing leadership skills and responsibility are part of the overall objective and bypassing the designated Captain is disrespectful and counter productive. Ralph's suggestion above, of moving to within earshot of the HC, and explaining the options to the Captain carefully and completely, allow the HC the opportunity to fulfill his responsibility of developing his Captain.
This consideration is not necessary for the majority of penalty options, but the Referee should be aware of situations where ANY appearance of confusion or doubt becomes apparent in the decision process and take practical steps to eliminate such problems. As suggested, moving to where the HC can "eavesdrop" on the explanation of complicated and/or confusing situations is appropriate, practical and an inconspicuous manner in which to avoid unnecessary problems.
The purpose of explaining options is to assist the decision maker to understand his choices, and there is no limit to the number of explanations necessary to satisfy that objective. Our responsibility is to assist a student athlete to understand his options to be able to make an informed decision.
Of course a side benefit to respecting the responsibilities of a Captain, is having that respect returned when the assistance of that Captain may be extremely helpful in dealing with other situations involving his team.