You are aware that you can call functions from other objects directly without need of interfaces? Because it sounds that you forcing yourself to use them
Since you got MainMenuItem class (Blueprint is class same as C++ class) which you could spawn from MainMenu manager and contain in some array right? if you keep MainMenuItem object in MainMenuItem varable array you don’t need interfaces, because you can call functions of class MainMenuItem with variable as a target.
Interfaces are not made for communication, they are for relating unrelated classes which has same function