Think safety first and foremost. Put the car seat of the child who is going to need you the most wherever it's easier for the driver to reach, esp. when s/he's the only adult in the car. You'll probably need to reach the toddler more often for now. I also like that the toddler on the passenger side gets out onto the sidewalk. Plus, he might? be able to help you by putting the pacifier in the baby's mouth...or maybe it's too far away. Food for thought--If you kept him in the middle, he could definitely help with the baby a bit ... guess you'll have to wait and see how he is with the baby, though.
An important REMINDER/WARNING of how dangerous it is to to pass things back and forth to children. (I'm guilty, too.) No matter how much we think we're in control, it is always a distraction, even if at best just a little distracting. A local mother and 2 of her 3 children were in a fatal accident driving down Main Street.
Congrats on baby #2!