I would take the box out of the parents' aviary/cage and boil any eggs that they lay. An embryo does not start to develop until the hen starts incubating the eggs, and she won't do that until she has laid the full clutch; you won't be hurting or killing anything. You can take the new eggs as she lays them, boil them and mark them with a marker pan so you know which eggs have been boiled.
You can buy specialised handrearing food which is higher in protein, fat and the vitamins and minerals that growing birds need:
Roudybush Hand Feeding Formula 24oz
This comes as a powder that you mix with hot water. You need a thermometer to ensure that you are feeding at the correct temperature - too cold and the babies won't accept the food, too hot and it can burn their crops.
It would be a good idea to find out who your nearest exotics specialist is. It's much better to know this in advance - in an emergency, you want to get the bird to an avian vet asap. The last thing you want to be doing is googling around for a suitable vet.
You can check the Royal College of Veterinary Surgeons for people who have postgraduate qualifications in treating exotics. "Specialist" is a higher level qualification than "Advanced Practitioner" but both mean that the vet has studied exotics extensively and has taken additional assessments in their care.
Specialists in Zoo and Wildlife Medicine:
34 Veterinary Surgeons found who are Specialists in Zoo & Wildlife Medicine
Advanced Practitioners in Zoological Medicine:
56 Veterinary Surgeons found who are Advanced Practitioners in Zoological Medicine