Strategy for regularly updating datasets from excel files
One method is to have two sets of tables (This1, This2, That1, That2, etc.), or a set of tables in separate databases/schemas. Either way, you now have SetA and SetB. Have a set of views that access one set of tables, say SetA. Perform the nightly imports to SetB. When the new data is ready to go, recreate the views, pointing them now to the SetB tables. The next night, use SetA to import.

The views will act as a software switch with an unnoticeable switch-over rate. And it should be dead simple to add this to existing Ruby script to coordinate all of it.