I ran this trigger a few times and saw that it massed workers too, I don't like this, is it possible to force this trigger to only run on an area with certain units instead of all the units the player owns?

Use 2 computer players with the same color. One owning the workers, the other owning the armies.

Strategic suicide will send all military units using a formal attack.
Random suicide will send every unit, including workers, to attack random enemy units.

It may be possible to temporarily give workers to player 12, run random suicide, wait a bit, and give the workers back.