Flat
With children, schedule one museum, one park and one flat stretch. Not a stamp list. Prefer flat ground: Cheonggyecheon, Yeouido, Seokchon Lake. Lotte World or Olympic Park, not both. The War Memorial outdoors will walk children for a long time. If that is the day's main event, do not add a palace. Do not put the palace, a Hongdae night and two towers on the same day. When they are tired, stop. Do not use Line 2 to collect the next district. Eat on the stretch you already chose. Do not transfer for another snack. When the flat stretch is finished, go back to the hotel. Do not use the leftover afternoon to add Hongdae. Snacks stay on the stretch you picked: the stream, Yeouido or Seokchon Lake, one of the three.