You need one macro, on each slave.
The macro is to assist the leader, so the slave is targeting whatever the leader is also targeting.

Once this is done, you need a keybinding, which is not a macro.
You'd press escape, go into the keybinding options, scroll down to "Interact With Target", and pick a keybind that isn't used elsewhere.

In practice, the main - master/active toon selects whatever you'd like the slaves/followers to interact with.
You then press your assist macro, so the slaves are all targeting what the master is targeting.
You then press your keybind to interact with target.

Done.
The slaves have interacted with target, be it a quest giver, flight path, mob to loot etc.
Without ever going to their windows to make a selection with your mouse.
Combined with Jamba, you can have your slaves mirror the masters flight path selection, quests to take, quest rewards etc.