Cute babies. I'm a bit concerned about your set up. Not sure what wattage you have for a heat lamp. Chicks generally do better with less heat instead of more! The brooder should be large enough that the chicks can get away from the heat to around 70 degrees. If they have heat everywhere, it delays their feathering out, and they are at huge risk of overheating. If you can get electric to the coop, you could brood them right in the coop with a heating pad. So much better for the babies, and also for you. Chick dander is a horror in the house. Check out this article: https://www.backyardchickens.com/a/yes-you-certainly-can-brood-chicks-outdoors
Thanks for the heads up on the feathering process. Just inside for a couple days to get used to new surroundings and eliminate any stress. The cage will be placed in the run outside after that till they've grown a bit. My Mom who was a farm Gurl, Says there were no heat lamps, etc in her day. They even did ok in the Pennsylvania winters. There is definately a learning curve to BYC!!!!!