I would think it's way too early. You may just need to get a bigger/taller brooder box. We use an appliance box on its' side that we pick up from the local Lowe's store. We put two window screens (old style, made of metal) on top to prevent escapes and it works great.
If you have a covered run and secure coop for them to live in once they're out of the brooder, you won't need to clip wings.
Also, if these chicks are for showing, clipped wings is a disqualification I think. Though, at the 4H fair, they'd likely just drop you one ribbon level instead.