I recently adopted 2 little 1 week old Pekins to accompany my larger 3-4 week old Pekin duckling. There is a big size difference between them. I've already introduced them and the larger duckling and he is very gentle with them but I'm afraid he will step on them so I will keep them separated. When is a good time that I will be able to keep them in the same area? Or will my larger Pekin grow too much for them to stay together?