My father actually just stayed at the Metro Hotel. It's very clean and well kept. Friendly staff, good design. Reasonable price. Excellent English.

Staying halfway between the airport and the center of Seoul, there's only one area of interest - Hongdae. Hongdae is a great, youthful neighborhood, but that's it out there. You'd have to go into central Seoul for the sights and even furhter to the southeast for Gangnam area.

Just stay in Myeongdong. If you have a small bag, you can take the train (take the all stop AREX to Hongdae and transfer to Line 2, get off at Euljiro 1- Ga...which they call Euljiro Ip Gu in Korean).

The easiest thing to do is to take the Korean Air Limo Bus 6701 to Lotte Hotel Downtown. You just cross the street from there and you're at Metro Hotel. There's also another bus to Ibis Hotel Myeongdong around the corner (and walk from there), but it makes a few more stops, I believe.

Myeongdong is really where you want to be. It's in the middle, so all the subway lines are there for easy transfer to get around. You're in walking distance of all the major tourist attractions. Short taxi rides to get around.