It didn't register at first, but when I went back and read your post again I realized you have breeds that are different than here.
so your birds are basically adult birds, if you want to add chicks probably not a good idea since you are just adding two.
I would try to find some started pullets if it were me. I would also try to contain them near the others for a time so they can see each other but not interact. After the quarrantine period put them in the coop at night while the others are sleeping.
as to what breed, you probably have a different assortment available compared to what we have here. I know I love my Barnevelders, which you should have available.