Here's one discussion on the topic I found useful from a 200's perspective:
child seat in 3rd row
Another IH8MUD search result for other tidbits related to car seats which may also help in your research:
Google
Variables such as size of car seat (or booster) will come into play here, which may theoretically let you put two child seats on the 60 portion of the 60/40 split 2nd row and allow and adult to enter from the front and access the 3rd row. But, it seems the 3rd row is not always best option for adults due to leg room, etc. and would depend on their agility to crawl back there. Alternatively, some kiddos seem to like crawling into their car seats via the rear hatch if you're wanting to place the car seats/booster in the 3rd row instead.
Hope this helps a little bit!