Hi Josh,
I'm not sure if you can update the status to not active with a workflow rule. However you can change the state of the of the workitem to draft.
Please add to the workflow the another action after you are creating the task which is:
Change State --> Draft
I believe you'll have to iterate on the subitems which basically means you'll have to change the Run On to Sub Items.
Let me know if that work for you.
Good luck!
Tamir