I'm korean and often visit Ren Seoul. The lounge door of Ren Seoul is always open and therefore you don't need to bring your room key for entering.

And a very kind service staff is usually standbying near the lounge entrance.

You should pay 25,000 KRW (exclunding service charge and tax) for your wife.

For your 6-year old kid, I'm not sure whether they usually require payment for such a young kid or not.

And on weekend, breakfast at the Elise Restaurent is served instead of BRF at the lounge.