Using Dollar, the drop off is in the garage right across the street from the terminal. If it were me, and it has been many many times, I'd just follow the rental car return signs and get rid of the car(s) first. If you drop off the families you'll have to drive all the way around the airport again to drop off the cars. Dollar is pretty efficient in handling the returning cars and then your whole group would just go across to the terminal for check-in.
Dick Taylor