K.Z.
I just got to Seoul on March 3rd and we just went through the process of finding off-base housing. There are very few available single family houses in Seoul. Most have older kitchens and bathrooms, plus you are on your own to deal with things and the landlord. There are "villas" which are apartments in a building with 5 stories or less and then highrise apartment buildings. We have a dog so we were initially looking at houses and villas, but we found a really nice highrise with a pool and went with that. The apartments are bigger than most of the houses. There are, of course some very swank houses but they are either far away or out of the price range the government will cover.
When you arrive, you go to the housing office to determine your housing allowance and then you start contacting multiple real estate agents. Make sure they know how much money you get so they show you the nicest places you can get. Different real estate agents have different deals in the same buildings because apartments are often owned by individuals and managed by a company. If you don't have a car, make sure it is near the subway or close to base. You have to have the lease approved by the housing office before you sign it.
There are playgrounds on and off base and even a Gymboree (not the clothing store the one where kids play). I haven't been to it, yet, but I drove by it today.
Korea is great. I am really enjoying it so far. In-processing can be a bit of a pain, especially if you are a civilian like my husband is because civilians have different procedures, but things are working out. If you are military, your options are more restricted on off-base housing so be sure to get the housing brief to make sure you know what you are entitled to.
You will be staying at the Dragon Hill Lodge when you get here. There is a regular Wednesday playgroup that meets at 10:30 and the DHL playground. I stumbled upon it accidently. Seoul is very modern and has a lot to offer. You and your son will have plenty to do.
I don't have any comment on the yellow dust. I haven't been here long enough. When it is really bad, you are advised to stay inside, but it hasn't been that bad since I have been here.