It's a tough call...
Can I get a car seat back there? Yes. A forward facing seat for my 14-month old. Does it have latch attachments? No, but I can use the seat belt.

Can my 6-year and 7-year old back there? Yes.

The third row does have cup holders and air vents (if you order the rear seat climate package).

The 2nd-row seats do recline and move fore and aft when getting the third row option.

Can the kids who sit in the third row see the DVD screen? No.

Can all three kids (one in the car seat) fit on the 2nd row? Yes. But I ordered the third row because you will need it in emergencies.

Bottom line- the Merc GL450 has the best third rows in an SUV. They have power up and down; the front passenger seat automatically moves forward when you incline the 2nd row seat up to gain access to the third row.

But the GL does not drive like a BMW and its reliability is questionable...so get the X5.