Good breed selections. They will however grow faster than you might think. So, not only do you want to be ready for the new chicks when they come but you will have only a couple of months to be ready for their outside pen and environment. Most of the online hatcheries have pretty good step by step instructions on their sites about how to take care of new chicks. I am guessing you are getting day old chicks so your heat lamp should probably start about 18 inches or so above them. Get you brooding area all set up at least a day before they arrive so that you can have the heat lamp on and check the temp. The first week about 95 degrees is recommended. Then raise the heat source (which lowers the temp) about 5 degrees a week until the brooder temp and the ambient room temp are the same. At that point you should be able to eliminate the head lamp except if it gets extremely cold.
Make sure you have chick starter (non-medicated if you had them inoculated), feeders and waterers, Put down a layer of shavings or other bedding in the brooder and cover it with paper towels for the first few days (this assist the chick in figuring out that feed is food and shavings are not). Have on hand some electrolytes (you can get individual packets that mix with their water) and give them that the first few days to help reduce the effects of stress that they will probably be experiencing.
If your box/brooder is 4x7 that will provide 28 square feet which should be ample for most of their time until ready to go outside. You can move them outside after they are fully feathered (I would not move them earlier since it is coming up winter).
Have something (1/4 inch fence fabric, chicken wire, netting) to cover the brooder box with. After a couple of weeks they will experiment with flying and you will have to chase them down if they get out before you are ready.
Good luck to you with your new chicks, they are a real pleasure.
