Started using UUID's as primary key, would like to execute union of entities with BigSerial Primary Key

Some of my newer tables are now using UUID type fields as PKey and older tables are still using bigserial. I have several tables (let’s call them entities) I would like to query returning the primary key in the result (using a UNION). What is the most efficient way to return the entity_id’s? I am assuming a simple CAST would do the trick, but this is to handle a sitewide search which requires it to be as quick as possible.

    select entityA.a_id::TEXT as entity_id from entityA
    union
    select entityB.b_uuid::TEXT as entity_id from entityB
    union
    select entityC.c_id::TEXT as entity_id from entityC
    union
    select entityD.d_id::TEXT as entity_id from entityD
    union
    select EntityE.e_id::Text as entity_id from EntityE

Any recommendations?