This also led to a maybe new kind of parenting moment: I (gently, they are quite young) explained to my youngest that their power button pressing was what had prevented their older sibling from adding pizza to our shopping list a few minutes later.
I'm curious whether my youngest loves pizza or pushing interesting buttons more. I'm sure I will find out.
Of course, their sibling's laughter upon realizing what happened was probably the strongest factor, toward future behavior.
If it gets to be a habit, I might have to disable that power button, after all.