The topic of child safety seat incompatibility with the Q7's head rest system has come up a few times now.
Audi's "brilliant" engineers decided to replace the easy-to-remove headrest system found in all other Audis with a fancy, slightly over-engineered folding headrest system. Given the lack of adjustability and the inability to (easily) remove, some car seats simply could not be installed in either the 2nd or 3rd row seat and has even registered at least one complaint on the NHTSA's website.
With the impending arrival of our third child (yay me), I finally got off my lazy behind and looked into how to remove the head rests. The 2nd row head rests can be completely removed in less than 5 minutes per side. The 3rd row head rests are removed similarly, but because of the "auto fold" design, they are attached via a cable that runs on the inside of the seat. To remove them per Bentley manual, you actually have to remove the entire bench and leather padding/upholstery. I was able to get them out another way and have photo documented the process I used further down the page.
These pictures show how you can remove the head rests from both 2nd and 3rd row The last picture shows the-still-connected 3rd row head rest that I temporarily flipped around to make room. If you want to remove them from the 3rd row, you need to disassemble the headrest bracket to slide the cable mechanism out.
Third row seat head rest removal:
*** WARNING: The head rest is attached to a bracket at the base of the seat that runs through the inside of the seat. Do NOT pull too hard on it or you WILL dislodge it (don't ask me how I know :-( ) ***
Picture of head rest completely removed. You can use the trim piece to cover up the opening if you choose...