No, don't put them in with the hens right away. The chickens will probably go after them, and possibly kill them. You need to keep the new chicks in a brooder until they're full feathered, at least 6 weeks old, and then introduce them slowly to the new hens.
The way I introduce babies into the flock is pretty simple. I put them in a wire cage inside the hen house, up against one wall, so there is at least one side where the big girls can't get to the little ones. Kind of a time out place, if you will. Let them stay in there full-time until the big hens aren't paying any attention any more. They will pick at them through the wire at first. After that, I sit in the coop with them for a little while each day, and let the little ones out so I can protect them from the big girls. Once things seem peaceful enough, you can leave them unsupervised for longer periods of time until they're fully integrated. There is likely to still be a little picking and bickering while they work out the new pecking order.