Hi Mike,
Just so I understand correctly, you are creating work orders for the servicing jobs already, correct?
What I am envisioning is that you can customize the work order screen to create a follow-up activity for yourself to send the postcards. All of the relevant details of the post card activity can be gathered from the original work order and set to two weeks before the next date of service. You could also use the "Cause Reminders" option for the Activity Type (create a new one for your post card activity) and setup Automatic Reminders to get an email reminder.
To group the work orders, perhaps you can use a custom field or tags to group each customer by a specific region. This whole project will take a bit of customizing, but it wouldn't be as complex as it may sound.
At a stock level, there isn't much you can do that would match your workflow and reduce what you're already doing. A work order is an activity, so if you showed it in the CRM, you can create a follow-up from there for your post cards. This would be similar to what you're already doing with the To Do event.
For information on Customization, I'd suggest to go through the Customization Webinars to get a handle on the customization. You can also speak to one of our in-house consultants or a Method Solution Provider for help on a project like this.
Let me know if you have any questions. Hope this helps.
- Adam