No! Do not use cedar...the oils are toxic to a chick plus they can inhale them. I line my brooder with 2 layers of paper towels and then put an old t-shirt or something in the corner for them to nestle on. Just toss when you are done!
Never use cedar around any animal. Especially in smaller cages or tanks with little ventilation. Kiln dried pine is better than regular pine. Pine does contain the same toxins as cedar just in a lower amount. Kiln drying removes a lot of it.