It sounds like the all-new 2016 Mazda CX-9 is a great fit for what you're looking for. Third row, but not too big a vehicle, and good mpg for such a vehicle. Usually I'm wary of all-new vehicles, but Mazda's record is pretty good with them. That said, it wouldn't hurt if you could wait for the 2017.
The Kia Sorento might also be worth a look, as these are relatively compact and driver very well. My concern with the Kia: owners have reported a fairly high number of generally minor issues in our survey.
The 2017 GMC Acadia is likely the size you're looking for, but an all-new GM product in its first year is risky.
If you feel that reliability is the absolute top priority, then the Toyota Highlander is the most likely to be problem-free.
Roomier than all of the above, but another all-new 2016 with a relatively high reported repair frequency: the Honda Pilot.