If your temps are warm they should be able to be outside now. You want to be careful mixing babies with adults. Personally, i wait until chicks have grown to about the same size as the adults. At that point i put them in a cage inside the pen of the older ones for several days to a week, so they will get used to each other, before fully integrating them. You want to be extra careful with silkies, as they could be easily killed by a peck on the head from an older larger bird.
You may want to build a small secure coop for them so they can be outside during the day. Or maybe put them in a rabbit hutch inside the pen of the older chickens. i have a small group of chicks that i'm keeping in a flight cage. i put their cage inside one of my chicken pens during the day, then move the cage into our shed at night for protection.