If you are flying from Singapore to Korea with kids, the biggest packing mistake is assuming you only need “warm clothes” or “a few extras.” Korea is not hard to pack for, but it does reward planning: winter can be dry and sharply cold, summer can be humid and rainy, and family days usually include a lot of walking, subway transfers, snack stops, and indoor-outdoor temperature changes. Pack for comfort, weather swings, and fast-moving days, not for hotel photos.
For most Singapore families, the smartest approach is to build a modular bag system: one carry-on for documents, electronics, medicine, and one-day essentials; one checked bag for shared clothing; and a small day pack for the parent carrying wipes, layers, snacks, and spare outfits. That setup keeps airport transitions simple, gives you backup if one bag is delayed, and makes day trips easier once you are in Korea.