Im sure they would do just fine. My 13 week old bantams have done well in the 30 degree weather we have had and they are the size of my 6 week old marans chick. If you feel more comfortable you could add a heat lamp. How many chicks do you have?
if it's in fahrenheit, it seems to be so cold outside, but since they're inside coop, I think they should be fine, especially if you provide them with incandescent lamp (hope the name is right, kind of lamp that produce so much heat with high energy consumption, real cheap light).
Last year I put 5 week olds in my grow-out coop with no heat. Night-time temperatures were in the mid 40's Fahrenheit. About three days later when they were 5-1/2 weeks old the night-time temperatures got down to the mid 20's F. They were not in a direct wind in that coop and were fine.
If you provide heat, realize you are doing it for your benefit, not theirs. They don't need it. And please be careful. Don't get them too hot and don't burn your coop down.
I'd just keep an eye on them. It will take a few days to toughen them up but I wouldn't add heat at this point. My chicks born at the very end of August just made it through Brutus just fine. We had sub 0 temps and days of wind. They did have mom but it was very cold. We had temps of 32°f when they were almost bare.
If you want to do something for them, put out something for them to crawl into. Mine slept in a coffee can for the longest time. They might just need something to hold their body heat close to them.