I just got two new parakeets. Any way I can make them feel more at home?

I just got two new young budgies. They are yellow-lightgreen and the seem nervous by the other four. I'm worried that they might get treated like our Dusty, who died of a broken leg. My two girls would push Dusty down and wouldn't let him get on the perch. We have a huge cage now and there's plenty of room, but I'm afraid that the new birds won't get used to their new home. Any help?