How should i tell my dad?

okay so I'm 13. I might go out with this boy named devin he's 15. It isn't official yet but I want to know how to tell my dad we're going out. I HATE lying, so that isn't an option, I'm allowed to have a bf and all but my dad will tease me and the other 2 relationships i was in weren't really real. Me and Devin have already kissed and idk if my dad knows or not, cuz it was a a friends house. I plan on having my dad meet devin pretty soon after we go out (if we do) and not hiding him like my other two. I need to tell him as soon as i find out if we're going out or not so if i ask to go to the mall with devin i dont have to make up some lame excuse, and i want to feel comfortable with havning devin come over to my house and not have my dad over my shoulder the whole time, he knows im reliable and trusts me but idk what to tell him or how to bring it up. He was in my myspace last night reading my msgs and read about when i was talking to my friend about asking devin out so i think he knows that much, im mad cuz he invaded my privacy, but i have nothing to hide or anything. i want to know now so if and when we do go out i dont have to worry about it then, should i avoid kissing infront of him?