Can I programmatically generate reports that are emailed as Excel docs from SSRS?
Ini. My first thought here is that you could use a List control to iterate across Districts. SQL Server MVP Jes Borland has a great intorductory post on Lists here: http://jesborland.wordpress.com/2010/11/17/the-power-of-reporting-services-%E2%80%93-lists/

Inside the list control will be a rectangle. By setting the Page properties of that rectangle, you can create yours tabs for each District, dynamically setting the Page Name property to an expression that returns the District.

You could configure your dataset (ideally, a stored procedure) to take the Region as a parameter and then you can run this ONE report for each of your Regions and they will all work the same and keep you from having to create multiple copies of the same object.

Assuming I understood your question correctly, this should get you moving in the right direction.