So no chance of installing child seats in both rows of the 7-seater? Also, is it possible for someone to enter/exit the 3rd row when (multiple) child seats are installed in the 2nd row? I'm guessing no on that one too.
Sounds like this variant is only going to be useful after the youngest children outgrow car seats and before the oldest get very large. A fairly small window of time.
I think you could get child seats in all 2nd and 3rd row seats, but they would have to be narrower seats and would still be very squishy.
The 3rd row could fit two boosters and even possibly a smaller toddler seat by itself. Again, even though they might fit and you can secure with seat belt instead of Latch, I would still not recommend having one back there often due to the hassle of strapping kids in and legroom that would be eaten up from the 2nd row.
Also, you cannot slide either side of the 2nd row forward with a car seat secured. If I had two seats in my car on the regular, I would probably put one behind driver and a second in the passenger third row. That way, you can slide single, right 2nd row forward to access rear car seat. This is assuming you need the additional two second row seats for other kids, so minimum four kids in the back. It could work, but just would be squishy.