Should i tell my family im an atheist ?

[AtheistPhil]

I don't see the point of telling him you're an "atheist", it's just a label and your father surely has prejudices against this particular label. I think your futur actions will speak for you. I guess you don't go to Church anymore so you're already acting like an atheist, what's the point of telling your father then ? He might think you're not religious but still catholic and that's a good middle ground for now.
You should not hide your criticism of his religion but don't label yourself anything.