Hi, I know it's been like two weeks since you posted this, but just in case you're still having the same problem I could tell you how I dealt with my problem that was pretty much the exact same as yours. I don't live with my parents anymore since I study in another city so I don't see them very often at all. After I met my girlfriend I wanted to tell my family about her, but I also wanted to tell them all at the same time and stuff like that. At first I figured I'd wait till I see them all again, but I realized that would take too long, so I simply arranged a casual little video call on Skype where I could talk to my mom, dad and sister at the same time. We just started the conversation like any other, but after a little while I told them that I'd found this super amazing girl that I've been together with for the past two weeks or so. They all took it really well and it felt great afterwards.Ugh, it is so much more difficult than it should be. I attend school away from my home town, so I don't get to see my parents often. But I don't really want to tell them over the phone. Bit I also don't really want to keep it from them until I see them again so I should tell them over the phone. But I don't really know how to say it, and I want to tell them both at the same time so it would have to be on speaker phone. GAH!
Sorry for the rant.
Of course you might have already solved this problem, but I figured I'd share my story in case it helps any. ^^