This is more common than you think. I was appalled when I heard my "friend" was doing this with her kids. She explained it by saying "it was more confusing for them to see us loving each other during the day but not showing that they are in love by sleeping together at night". It's just crazy, and selfish.
You could ask them what they think about it. Then tell them what you think about it, and tell them what God thinks about it. Your kids are smart, and they will know what's right.
