Just another person's opinion on the following:
"I don't think it is worthwhile setting up the ability to switch from LHCP to RHCP or vice versa if the spacecraft has linear antennae"
My personal experience says that if your goal is to maximize your horizon-to-horizon communication, then you need the LHCP/RHCP switch. When doing an ARISS contact with the ISS, which uses a linear antenna, switching polarity was the difference between a weak or non-existent signal and one that was full quieting. The ionosphere does strange things to a signal (Faraday Rotation), that results in it taking on the characteristics of a RHCP or LHCP signal at times. If your antenna happens to be the opposite at that moment, then you will experience a very deep fade due to the mismatch in polarity.
Certainly working the ISS for a room full of kids is a different thing -- you want them to have the best possible experience and recognize that lay people are not good at digging signals out of the noise. Your requirements for the best possible signal levels at all times is higher than during casual communication.
If you are a horizon-to-horizon person trying to maximize your contact success then the polarity switch will make sense. Otherwise skip it as Chris suggested.
73, Bob, WB4SON