Do they have a cell phone?

If you are sure they will arrive before you do, before you arrive have them walk outside and pick a door number that they want to meet you at. Then they can go inside or wherever they want. When you pass through the toll booth, pull over to the side of the road (using hand held cell phones while driving is illegal in Chicago) and phone them to ask which door they will be standing by. Then drive to that door to pick them up.

Otherwise, there is the Kiss & Fly area in Remote Parking Lot E where the Airport Transit System (ATS) train line ends and the buses stop. The ATS is out of service until November, but there are shuttle buses from Terminal 5 that will take you to Remote Parking E. To access the Kiss ‘N Fly area from I-190, use the International Terminal exit to Bessie Coleman Drive. Turn left at the traffic light on Bessie Coleman Drive and follow it north to the Kiss 'N Fly entrance. You are not supposed to wait at the Kiss & Fly, but hardly anyone uses it so you won't get in trouble for a SHORT wait.