The third row is not easily accessible if you have car seats on both sides in the second row. And you can't put car seats in the third row. I have 2 car seats and if I need to put a visitor in the third row I find it's easier to have them climb in through the rear tailgate.
Ideally you could find one with the console in the middle of the second row and remove the console allowing passengers to climb in and walk back the 3rd row between the car seats, minivan style.
As far as potential issues, it would be nice if the plugs had been recently replaced but that's unlikely on one with under 100k miles. Just have a mechanic thoroughly check it out.
I don't understand the problem with having 2 infant seats. My son has his 2 year old in a car seat in the middle of the second row, and it works fine. He is about to become a father again and expects the second infant seat to be located on the second row 2/3 split bench behind the front passenger. The single seat (1/3) behind the driver is free to move for easy access to the very spacious 3rd row seats.
According to the Owner's manual for my son's 2007 Explorer EB V8 (7 seater with 3 rows) all 2nd and 3rd row seats (total of 5) can accommodate a child seat with tether.
Spark plugs are a two piece design with a very long section that accumulates carbon from combustion deposits. The torque required to separate the plug is 35 lbs ft and this can easily be exceeded by the friction of the carbon. The solution is a carbon dissolving fluid sold by Ford and a slow turning in and out of the plug until removed. Late 2008 models and later have a redesigned head that resolves the problem apparently.
The 6r60 is a very strong automatic transmission, but its initial programming for 2006/7 models can be less than smooth. A reflash with a later version of the software will usually fix it. The trans was updated to a 6r80 (increased torque loading to 400 ft lbs) in the 2009 and 2010 models, and very late build 2008 models.
The 6r60 does not have a conventional trans oil dipstick. So checking and replacing the fluid is not an easy DIY procedure. It uses Mercon SP fluid and the cost is the same as any other trans service.
The exhaust manifolds can warp and the studs break causing a slight noise and poor performance and fuel economy on 2006 through 2008 models. Due to access problems the repair can be expensive. I do not know if this was fixed on 2009/10 models.
The basic transfer case is AWD set at 40% front and 50% rear and there is no lockout. Higher end models have the torque on demand (TOD) transfer case (with AWD) and a lockout of the planetary gear differential. The TOD can be a one speed or two speed. The one speed uses the message center display to set and release the differential lock. The two speed transfer case has 3 buttons on the lower part of the center dash console, to select 4x4 Auto, 4x4 High Locked and 4x4 Low Locked. The "AWD TOD 2 speed transfer case" sounds like the one you need and is fitted to my son's 2007 EB V8 model. All 3 systems are sensitive to tire size, wear and inflation pressure, due to the AWD, roll stability and vehicle stability systems.
You may like the optional auxiliary rear climate control system. It is mounted in the back and controlled from the console over the rear view mirror. It allows heating and cooling of the 2nd and 3rd rows from auxiliary vents in roof and floor. The driver has control of temperature, fan speed and discharge from ceiling vents or floor vents.
You may like the power running boards on the 2006/7. They lower when door opens and raise when door closes (works with all 4 doors). The system allows easy entry (even for a 2 year old) but gets up out of the way when the door closes. Looks like a good feature for off road. It needs lubrication of the motor bearing, gears and joints on occasion.
The frame is completely boxed and very strong with numerous lateral strengthening members. The major components have good ground clearance and coupled with the independent suspension front and rear it should work well in off-road terrain. But it depends upon how severe the conditions are that you anticipate off road.
Good luck.
