Mechanical Shabbat Timer

Question

Is it ok to move the pins in on one of those mechanical Shabbat timers on Shabbat? My 3 year old can't fall asleep without the light on so we have it on a timer, but frequently he'll mess with it before Shabbat and it'll either be on when it shouldn't be or vice versa. If we move the on or off pin is this permissible since the timer is moving regardless and we're not actually directly affecting any circuitry?