During this past plebe summer, several families on the USNA Parents' ListServ talked about the challenges of plebes phoning divorced parents, because there really isn't time for calls to two destinations. If you try a 3-way call, be sure both parents practice beforehand -- it's not always straightforward for everyone. Also, "scheduled calls" don't always happen on schedule -- or at all -- so it can be frustrating to have a group sitting around a phone waiting for it to ring (especially if group members don't get along).
Sounds cheesy, but I sent my plebe some stamped, pre-addressed "multiple choice" self-mailers. He inserted a few jokes among his check marks -- it was great to know he could still ridicule himself, and his mother.
By the way, I think it's wonderful that pre-plebes are thinking about this, especially if parents don't get along. Maybe you can think of some clever version of drawing straws re: the first call, w/ the agreement that both will promptly email each other re: content of your conversation.