This is the hotel we have selected for the remainder of your stay, from October 11th to the 18th (or longer if you wish, please let me know). We are arranging for a bus to pick you up from the wedding venue and bring you here and also a bus to take everyone bus to the airport. If you do stay longer this bus won't be available for you, however there is a normal airport bus that visits this hotel frequently.
You can check out the website here: https://seoulgarden.co.kr/EN/
This is the standard room for 2 adults. pricing works out to $200.00 a night (weekends are more expensive).
https://seoulgarden.co.kr/EN/accommodation/standardD.asp
This room can accommodate 2 adults and 1 child (maybe 2). 4-person rooms are available but only for 2 adults + 2 children, and there are only two such rooms in total.
https://seoulgarden.co.kr/EN/accommodation/standardFamilyT.asp
The hotel is located in the Mapo area of Seoul and right next to gongdeok station which will be your gateway to Seoul. From here all the places you want to see (Hongdae, Gwanghwamun, Myeongdong ect) are easily accessible. Additionally the area of Mapo is filled with great restaurants (particularly BBQ).