5 week old ducklings and chicks

As the title suggest I have 3 black australorp chicks and 3 khaki Campbell ducklings that are 5 weeks old. Both are out growing the brooder and the bathtub. It has turned cold here in the mid south and I am wondering when they can go outside and not be compromised due to the cold. Chicks have most of their feathers and the ducks are getting theirs. I have 3 7 month old barred rock chickens and one 4 month old white maran outside and they have handled the burst of cold that we have had. I'm new to the poultry homestead and want all my girls to be happy and healthy. What should I do? I'm not in a hurry to get them out of the house but would love some feed back so I can do the right thing for them. I've never had outside pets so the cold weather has me really worried. I'm the type person who puts sweaters and coats on my two dogs in the winter when they go outside.

 

Thank you so much for the information and the websites to check out. Since this is my first time owning chickens and ducks I'm treating them like a first child. You know nothing really and over think everything!!! Lol!! Plus your suggestion of weaning off heat is a great idea. Hadn't thought that far ahead. Lol!!