Oh my I do not know what to tell you. But I guess it is good they are not fully bonded to you because that could be even harder on them.
You will have a lot of work to do when you get back, I would think basically like starting over like they are brand new to you.
Have your parents play with them if they are willing. Even playing with them with something like a feather wand trough the cage will help keep some socializing with people.
Sorry that you will be gone from them so long.