A Korean drama where the couple get married and have children ??

There are some really nice dramas that involve couples and children so I would definitely recommend you:
1. Wonderful life: it's one of the cutest dramas I've seen and it's about marriage and child
http://mydramalist.com/korean-drama/321/wonderful-life
2. Prime Minister and I - marriage and children ( maybe not exactly what you're looking for) but I highly recommend it;))
http://mydramalist.com/korean-drama/8129/the-prime-minister-and-i
3. Autumn's concerto - It's not k-drama, but it's one of the most amazing and heart warming taiwanese dramas I've ever seen so it's worth giving it a try
http://mydramalist.com/taiwanese-drama/81/autumns-concerto

i just finished watching A Thousand Day's Promise. the main couple gets married and has a child with a lot of adversity in their relationship.

Queen of Reversals is exactly what you're looking for. It's an exploration of a marriage. They get married pretty early into it and have a child together.

Love Now (goes romantically) Empress Ki (goes not romantically)

Loving You A Thousand Times..
The lead couple married in the middle of the story and there is also a child involved. You can check it out. It's also a great drama.

You can try "tomorrow with you". They don't have kids in the drama but they get married by the fourth episode. It isn't one of my favorites but it's a good one. ^^