Ever since one of my hens raised some chicks, I will NEVER raise chicks on my own again!! They are such wonderful mommies! When my hen raises chicks, I use to put out a crate with wood chips in it but she never used it... she always prefered to sit with her chicks in a corner of our coop so now I don't do anything differently as far as housing. There are only two things I do differently when I have chicks in the coop:
1) I put out chick starter feed (my main feeder hangs off the ground so chicks can't reach it anyways and I do not mind if my older chickens eat the chick feed as well - to me it is ok since I prefer not to seperate anyone).
2) I change my water containers to ones the chicks can't drown in (normally I keep out buckets full of water)
That's it! Your hens should keep your chicks plenty warm - they will stay under their momma most of the time in the beginning.
Good Luck!