So we have 2 people who have never likely been in a light airplane and you are going to have them climbing over the seats in the tightly confined space of the Pa 28 cabin
This strikes me as a really really dumb idea. All it takes is for one of them to push the control wheel, kick the instrument panel, hit the door handle, get stuck twisted half way etc etc and you will be deeply regretting doing this
I have never done an inflight seat change in a light aircraft and think it is inadvisable under pretty much all conditions.