Lying is a premeditative action. I'm curious to hear how a person "accidentally" lies. If someone asked you what you ate for lunch and you said a hotdog... only to remember an hour later that you had a hotdog yesterday and a hamburger today, you didn't "lie"... You were mistaken, unless you knew you ate a hamburger and deliberately said "hotdog".
I don't know why you are rationalizing parents lying (not pretending and make believe) to their children... This is exactly why there are people who claim to be active homosexual and Christian... They rationalize their love for someone of the same sex by saying that love comes from God... who cares that God is adamantly opposed to it...?