Honestly (hope I don't get booed off here)... they do start to smell "chickeny" as they get older. I'm not talking about the brooder smell, since the clean pine shavings smell like pine shavings. But the chickens do have a certain, distinctive smell. Just want you to be prepared.
Personally, 1st week I love having the babies inside. By week 3-4 though.. I'm ready for them to move to a much bigger box in a much less used place. That's when they move to the huge brooder box with the heat lamp in the garage. I love my chicks, but they do get rambunctious.
So... personally I'd keep them in for the first 4wks, then move them to the henhouse (if they are your only chickens) with the heat lamp. As long as it is the correct temp under the light, they will gradually spread out further and further.
I bought my group in mid spring, and here there are some similarities in temp between that time of year and this. And I moved the 'kids' out at 4wks. They were fine (but I was a mess at first!!).
-Meghan