Presuming you are making multiple sites not just list instances given the type you are adding:
Create your calender site as you want it, or the site that includes the calender, with all options configured.
Create a new site off your site definition, then open up that site in Designer.
Go to: Navigation > Lists and Libraries > Double click category, and edit the choices as desired.
Then you re-save out your site template as a new site template with the following:
Navigate to your new base site, go to:
Site Actions > Site Settings > Save as Site Template
Input your Title, File and Group.
Then when you go to create a new site use your newly created Site Template instead.
All your configured options will be there and you can enjoy the benefits of simple replication.
The reason for a site, would be that when you create something like a calender then you usually are creating other lists and libraries for the same instance. Just changing the list definition will only help for creating new lists, this is why I didn't go down this route in the first place.
If your site definition sites locally, the same edits can be made to the Schema.xml of the Events list for the Calender.