Taking elderly in-laws (86 & 88 ) on 500 mile trip.

We used to take my mother for an all day, 400 mile trip to visit friends and relatives. She did well, needed some extra pain meds, but loved it. However, on the last trip she undid her seatbelt and we glanced in the rear view mirror to see her toddling to the bathroom @ 70 mph! We said *nothing* crossed our fingers and she made it, TG. After that, I rode back there with her. She died in 2011 at age 93.