Two infant seats = twins.

My girls are now 15 months, and the best advice I can give a father to be of twins is you MUST have them on a schedule from day one and you've got to stick to it. To the tee. And have them do everything at the same time...two babies, one schedule. When they sleep you MAKE your wife sleep or otherwise she'll be screaming after a couple weeks. And it's a good idea for you to do the same. Learn to swaddle them tightly, they love it, and you don't want any arms moving around while they'e sleeping or they'll wake up. If your wife is planning on breast feeding and she has any trouble with it have her see a lactation specialist. I could go on and on but those would be my basics in preparation. Oh, one other thing. Forgo the basinettes and start them in their room from day one. Your few hours of sleep will thank me.
Your gonna love it, bro. It's a hell of a lot of work and you simply can't understand it unless you're a parent of multiples, but it is incredibly rewarding, interesting, and amazing to watch two little beings develop. Quite simply, your life will never be the same.