So Iran doing nothing= emboldens it's enemies from pushing its bottom line and also weakening the current regime internally from the persistent and lingering enemies (Shah remnants and others). Iran doing something = invites an increased attack not just from its omnipotent enemy within the region but also from the superpower America.
What is Iran to do? Stay impotent? Collapse the leadership and become just another Arab state under the leadership of the west?
That's why I'm saying they walk a fine line. They have to demonstrate an effective retaliation, but not large enough to trigger US involvement.
But I think it may be moot because Israel seems to be actively trying for more escalation, even if Iran did control their response Israeli will try to one up them in the next round until they bring uncle sam into the fray.
It's too early to say at this point, but if the retaliation is limited to drone strikes, then this is intended to impart as few casualties as possible while offering a way for both countries to de-escalate.
A retaliatory strike intended to hurt the enemy would amount to something akin to firing multiple waves of ballistic and cruise missiles and timing to have them arrive on target simultaneously. Iran probably knows and expects to have most of the drones shot down en route. That allows the Ayatollahs to save face for its people while preventing a serious escalation with Israel that will put its leaders in a significantly more precarious situation. Israel probably expects this as well and sees this as a stepping stone for de-escalation.
Remember when Iran "retaliated" against an US airbase following the killing of Soleimaini? Same kind of flavor.
Personally I think Iran has to demonstrate effective retaliation in this case, different from the last one against US. Lets wait and see