If the coop is assembled and the heat source can be moved outside with them, yes they can all go out immediately. I brood outdoors in a no-clean set up as soon as I get the chicks, with a heating pad as the heat source. My latest batch...
They can definitely spend some time outdoors during the day. For your peace of mind and to ease the transition, I'd do gradually lengthening periods out. Make sure they have some place they can shelter in for shade or protection from wind.