Bill is right. You're pretty well maxed out with passengers & cargo in that Mercury. A tent might be in order. Towing a trailer (of any size) could be putting all those people in danger. It would be very difficult for that TV to make an emergency stop.
I weighed my 2720 fully loaded and it was right at 3700# and there are just 2 of us. Carrying enough cargo for 7 people, you would be hard pressed to keep the trailer under 4000# (the GVWR on our 2720 is 3956).
You need a TV with a tow rating of about 6500#. You may be able to find one that has a tow rating of 5000# and a GCWR high enough to carry all those people and gear. A ford Expedition or Chevy Suburban might be worth looking into. The Nissan Armada has a tow rating of 9000#
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