I would take a short sleeve for summer and long sleeve for cooler weather. I vote for #7 as well with 1968-2018 added to bottom.
Every member should consider buying at least one shirt to acknowledge this milestone, let alone the MOA club #1. Then a group photo of ALL members in shirts at a chosen scenic location would be a nice thing to hang on the wall of your favorite place.
A bonus would be a group photo including ALL members and ALL bikes shot from a drone (anybody own a drone?). As suggested ON magazine would also be a very cool thing to happen.
Maybe a topic of discussion at the upcoming planning meeting?