Here's another idea since the "waiting area" landside at T5 arrivals can get busy... As your friends exit Customs and pass the connections desks into the landside waiting area, if they turn left there is a bar nearly to the end of the waiting area (there is a large sign above with red letters "BAR"). I've used it before as place where whomever arrives first can have a seat and a beverage while waiting on the other party to arrive.