How do I tell my parents about my pregnancy?

I'm 21, been with my boyfriend almost 2 years and known each other much longer. He's asked my parents for permission to marry me (they said yes). I just found out I'm pregnant--and that is a good thing, since we've both been wanting to start a family. The problem is, how do I tell my parents? My mom will be thrilled of course, but I know my dad is going to be upset. I just graduated from college and he's going to be disappointed that I won't be going straight into my career, and I'm afraid he'll be angry and think I'm "wasting" my college education. How and how soon do I tell them?