Hi!! I drive a '93 Pathfinder that has been modified for towing, but your 2008 should be setup better right out of the gate. Since you have the SE, you probably have the 266hp V6 unless you opted for the V8. As the SE is rated for 7000 lbs, you should have no problem. Since the WD21's like mine have a more delicate transmission, I always make sure that it has had a trans fluid change yearly at a minimum. Looking at your shift selector, it appears on the left side just below the release there is a button. On my WD21, this is red and keeps it from popping in and out of overdrive when you are towing. I would check this out, and use it when you are towing if I am right.
Since I have toasted 2 transmissions on different cars over the year, I would make sure that you have a trans cooler installed, the larger the better. Nothing kills your transmission like hear. In line with that, if you notice your transmission is shifting frequently, try adjusting your driving habits and speeds to minimize that. If it continues to shift often, I would consider one or two rest stops along the way to allow the trans to cool. Make sure you install a quality electronic brake controller, and try not to "ride the brakes" whenever possible.
Hope your Dad enjoys his trip!!
Take care - Boothill2008
Sent from my SM-T813 using Tapatalk