韓幣兌港幣是多少?

I would suggest you should exchange in Korean Airport, since it provides a better rate than the bank in HK.

Before exit the immgration, there will be an currency exchange shop for you to buy Korean Dollar (WON). It should be around 100 HKD can buy 11400 - 11500 WON.

I would suggest you can exchange 1500 HKD, which will be enough for travel in Korea for 5 days for each person.

剛剛去完韓國，在當地機場兌115，貴左少少。