Totally depends on the aircraft and airport.
If it's a newer airliner with an automatic landing system, coming to an airport with a CAT III ILS. Well then a child could do it. Tower would just have to tell them which switches to flip to which knobs to fiddle and the plane would land itself.
Even short of that, I don't think it would be that difficult in fair weather, for the tower to talk even a complete rookie through it. They'd just leave it on autopilot down to minimum, then they'd only have to fly it the last 200 or 100 feet. Find an experienced pilot in the aircraft type in the tower, and they could talk them down. They would have plenty of time before actually taking the controls to do all the stuff like arm the spoilers, and bring down the flaps. It would probably be a rough landing, but airliners are pretty tough.