Creatives are just as organised as anyone else
Don't get fooled by the notion that creatives can't organise themselves: if they can organise themselves to make their way to work every morning, or to go on vacation, they can plan and organise their workload.
It's not about the capacity to organise their work, it's about the incentive to do it.
So instead of doing it for them, give them a reason to do it: how does it benefit them? What problem does it solve for them? It will free up some of your time and they will do it in a manner that suits them better.