Welcome to BYC!
Up until ours were ready to go into their coop full-time, we modified a dog crate and would transport our ten birds in the crate, which we set inside the run and opened the door for them to fly out of. They would play in their run/coop during the day (weather dependent) and then bring them in at night until we felt it was warm enough they did not need to be sheltered in there brooder in my insulated workshop. We did transition them by removing any heat source from my workshop for the two weeks leading up to moving them in to their new home permanently, but because of the insulation, it naturally stayed a bit warmer than their coop.
Pay attention to your chicks when you first move them in. They will tell you if they are too cold by chirping incessantly and huddling a little too much on top of each other.
Strictly speaking from our experience. I'm sure there are better ways of doing this, but I hope our experience can help!