Stone Devil is the designated driver in this situation, since Nightshade needs to spend a move action to get her shirt back on.  Stone Devil can technically drive while in his humongous form, but the added weight will impose a -1 speed rank penalty to the car, and he'll suffer a -5 penalty to vehicles checks to maneuver.  It would still get the group in range for long range rocket launcher and lightning strikes, though.  (and of course, making it rain will help as well.)