How should I tell my parents that I am moving out?

So the situation is that I current live in my parents home. I am 18 and a have a 7 month old baby. Her father and I have been together for about 3 year. I am in college and he is working. We are renting a newly renovated trailer and he has just moved in so I need to get my things together and move too before I have to jump back into school in a week. My parents are believe that I would be living in sin if I live with my boyfriend/baby's father; however, I do not believe in the same things(obviously). I do not feel that it is better with my and our daughter living with my parents when me and the father are in a great relationship and have this opportunity. I believe that it is wrong for my daughter and her father to have the relationship they do, which really isn't one, when he is torn by that fact. We are a family, unconventional I guess but family none the less. My main issue is ruining the relationship we have with them. How should I tell them I'm moving?