God bless you and your son!
if you are looking for the "best price", asking it in Korean Air forum might be the wrong way to go. While Korean air does offer a wonderful service from ICN (korea) to IAD (washington DC) NONSTOP, but they tend to be more expensive than one of American Major Airliners.
You should consider looking into Delta, or simply one of the website that gives you multi-quotes (expedia or yadiyada).. even if they aren't NONSTOP, you will find them much MUCH MUCH cheaper.