I would put the infant seat in the middle of which ever row is closest to an adult. We put DS in the first row, and niece in the back row, both parents sitting on each side of the kids, while the IL's drove one year.
We drive a Sequioa with Captain's seats in the second row which is where we put the carseats. The third row is almost always folded down flat to extend my cargo space in the back...for the double stroller and whatever else I need to put back there. Carseats can go on my third row though because in my car they're full sized bench seats that are capable of folding down 1/2 or the whole seat. I know the Highlander's 3rd row seats are itty bitty and I'm not sure how carseats would work back there if at all.
Re: Who has a 3 row SUV?
Yes, if there is a middle. I have bucket seats in my 2nd row so I put the car seat behind the driver.
We have a bucket second row, so there is a carseat on each seat. If we had a middle and one child, it would go there.
edit: You could put a carseat on our third row (Yukon), but my preference in 3rd row cars is to use the second row.