8000 lb trailer capacity less family of four, 600-800 lbs depending upon of kids are preteen vs adult sized teens. Puts you at around 7000 lbs max trailer. Maybe a bit less. To stay under factory gvwr of around 12-13000 lbs.
You can sit, as noted, you might be slowish. You won't be the first trying to pull at max, slow more than you think you will or should. Don't let motor lug, find RPM that engine seems comfortable towing at on hills. My 2014 4.3 and 2000 5.7 have no issues in the 3000-4000 relm when really loaded on a steeper 3-6% freeway grade.
Have fun
Marty