I have to apologize before answering this.
This question is, by far, the most dreaded question we wedding photographers get. There are so many that have gotten into trouble answering this very question, so brace yourself.
First off, how did 2 couples find you? Are you a pro? Do these B&G know that you are not a pro and that the wedding pictures can't have reshoots? Do they understand the value of having a pro shooting their once-in-a-life-time event?
So, I'm assuming you are going to shoot the weddings and no one is going to convince you that you're not ready. With 2 camera bodies, you may get away with using the lenses you have or can borrow from your Dad's. What camera body does he have? Because you will need 2 bodies. For the most part, you will end up using the 24-105L and 17-40 (large groups) and 50 1.4 for portraits. You'll need a good flash with a diffuser.
I can't say enough about practice and looking at the stickys for wedding photography here in the forum. We have a list of "to do's" before weddings, like checking to see if all you 5 batteries for your camera are charged fully, have 20 GB of CF cards, etc. There are so many reasons not to shoot these weddings, but if you are sure, you have a few months to prepare. I've been shooting now for over 5 years and I can tell you, I still don't have it down. There are about 10 really fantastic wedding shooters here, so I'll let them say a few words. PM me if you want to talk more. This is how I started too, so I don't want to discourage you too much.