Does S12 have access to the schedule as well? In my mind, it is imperative that all three of you have access to the schedule so S12 knows where he will be at all times and not be pulled in all different directions like a Raggy Andy doll.
When I was young, I knew my schedule because my late father and stepmother would post it for me. When they first got married and went on a honeymoon not long after my 3rd birthday, they gave the printed schedule at my pre-school so the teachers would crouch next to me as I marked "X" each day so I had a sense of when they'll return from their honeymoon.
This keeps every one honest and I think W would toe the line more with the awareness that S12 sees the same schdedule as you and W do.
Hey, who wants to come out looking like a "bad guy" for switching the schedule so many times?