I got my very first chicks October 2, 2009, and added a few each week for a month. (Uhhhh.... it just happened???) They started laying in late February. Because we did have a cold snap for a few days longer than is usual in this part of the state, AND I'm a doting first time chicken momma, I kept my chicks inside at night until the oldest were 12 wks old and the youngest were 8 wks old. I wanted to put them all out at once, so avoid repetitive bouts of pecking order problems.
You'll do fine. However, now that I've started with more chicks this Spring, in the future I will try to stick to Spring chick purchases - as opposed to Fall or Winter. There's just more opportunity to give the babies their little day trips outside, and the heat lamp usage in the brooder is MUCH less intensive.
Just my opinion - and I'm a relative newbie to chicken keeping.