Are there any laws in islam that tells us it is a must to have marital intercourse upon closed doors?

Assalamualaykum, If a kid of a couple runs into them during their private time who leave their door open, how should the kid respond in an Islamic way? Are there any hadiths and or qur'an verses mentioning this? I wish to say something about this to my parents but fear offending them, or better yet, how should I respond to this in an islamic way? because these types of things have not only happened once unfortunately. I know these sort of subject is taboo, however I believe that islam is the religion with answers to even the most lightest of things. please forgive me if I had said anything that may offend anyone, wassalmuallaikum.