Korean Name and Culture Check

I think I've got this right, but I'd like another couple of sets of eyes.

I have a Korean-American family. Mom & Dad were both born in Korea, but immigrated to the US over 20 years ago. Dad teaches at University of California, San Diego. His name is Kwon Jeong-ho. His wife is Choe Hyun Gi. Her mother also lives with them. Would her surname also be Choe?

Steven Kwon is the main guy I'm interested in. I have him named Kwon Seong-min. He has a sister, who named Kwon Ji-hye. I don't have an American first name for her. Do I have the surnames tracking correctly?

Steven and his sister were both born in the US. How do Korean-Americans handle their identity documents? Would his driver license say Steven Seong-min Kwon?

Also, how might Grandma react if Steven's new American GF bowed to her at their first meeting? Would she likely accept it for the honor intended? She's very old-school.

Steven is about 20; his sister is a year older. Would they be likely to go by American first names? His parents are in their 50s. Would they likely go by Korean or American names.

Thanks so much. Grandmother does not speak English, and all I've written about her is that she's pretty old-school (she'll make regular comments about Steven's long hair), and lost two sisters when Seoul fell, and her husband late in the war.

So her name will not (necessarily) be Choe, but could be, owing to commonality of names, correct?

How funny! The old Austin airport was named for my grandfather, and I still have a cousin in Georgetown. It really is a small world!