Why? If it's just for the ride I'd leave them at home, they will be stressed. If you have to transport chicks it has to be age appropriate so what age are they? Just 2 chicks can't keep each other warm so you will have to provide heat unless they are not fully feathered.
I brought 4 silkies from California to Maryland last summer. We put them in a plastic tub and everytime we stopped for gas, I fed and watered them. We tried to keep it dark while driving so they would sleep and then when we stopped to sleep we put them in the motel bathroom (still in plastic tub
) with the light on. They did great.
For a seven hour ride, just make sure they are warm and maybe stop every 2 or 3 hours for food and drink.