Honestly I would observe and see how it goes. Some hens/flocks will accept new chicks without much fuss. Are any of your hens aggressive? A good way to integrate babies (or any new birds) is to get a cage where they can be in the run with the other hens, so they can have visual contact of each other. Once this is done, if the hens pay them no mind they will be more easily accepted to the flock. Now, some people do as you did; put babies in during the night, so everyone wakes together as if they have been in the flock all along. Sometimes, it works! That's why I say wait and see in the morning but you MUST stay to observe to make sure they are okay! I would make sure to have multiple feeding stations because the dominant hen may try to keep them from getting to it. Try not to panic, they should be okay for tonight!