I did over 100K miles with an ext cab, then crew cab with my family of 6. Including when the 4 kids were adult size teens and we weighed in the 1100-1300 lbs range between the 6 of us! My twin sons are over 6' tall, daughtes at 5'9" and 5'10"........
Did I mention the crew cab had a 5 sp emanual tranny too! Having grown up in burb type rigs, family had a IHC Travel All, that back seat is not too comfortable! I do know another family that had 2 of there kids back there. Once 3 of the 4 kids got above 6'.......it worked, but was not great.
Frankly, a 4x converted van would be best. You can get payload, towing power etc. Especially if you can get a Dmax in the van. Not sure Ford has a van with a decent towing motor in it any more. ALtho the Frod matchbox former U-Haul cargo van I have at work, has just under 4000 lbs of payload. So that chassis would handle a family of 6, with 600-900 or so lbs of hitch weight. Not sure the motors offered would let you get over a 6-7000 lbs trailer with family loaded.
Marty