Mare think about having the dummy eggs on hand. It's a backup more than anything. I really understand your fear. That's why I do not give my birds a nest box. I know your girl laid the eggs before nest box in sight. @Cedardave is our resident breeder.
I do know the nesting birds and babies need a quiet place. You can still have tame babies and not hand feed if mom and dad are feeding. Cockatiel are supposed to be excellent parents. Co parenting is nice too I hear. Both you and parents feed. Do you have anyone in your area that breeds birds? May be a help to you. We are here for you too.