Just to be clear to
@TrueBagelMan , for myself (and I think the others... I could be wrong) I am saying that taking the Help action while Invisible would do one of two things:
1. the target can't see you, so you aren't really distracting it
2. anything you did that was "strong enough" to distract it, would constitute the same level of interaction
as attacking, and thus end the invisibility.
I would rule as such, personally, but that is my preference. If I played at a table and they went with a more "precise" (?) interpretation, that is fine as well.
-------
Now, strictly speaking, the terminology is precisely as you say and I think JC would rule likewise: The Help Action is not the Attack action or Cast a Spell action, thus you would remain invisible.
Many features can cause a creature to become invisible, and they remain so until they do something specific. Consider the following:
You become invisible until you MOVE or TAKE AN ACTION or a REACTION. If this warlock took the Help action, they would become visible.
So, by common ruling no, the familiar would not become visible by using the Help action.