You really need to weigh your new Expedition with all the people in it and a full tank of fuel. The difference between that number and the gross vehicle weight rating of your Expedition will set your maximum tongue weight. (Note that a properly set up weight distribution hitch will transfer 25-33% of the tongue weight back onto the trailer axles...) We are able to get away with a 900lb tongue weight, 6 people and 3 kayaks. That's because we're small people and we took the time to carefully weigh everything, did the math, and swapped our 800lb spring bars for 1200lb spring bars so as to get the proper weight transfer from the rear axle back to the front and trailer axles.
Here's how the math works for us. Our payload is 1600lbs. 1600lbs minus 600lbs of people gives 1000lbs of available payload. 900lbs of tongue weight with 270lbs (30%) transferred back to the trailer gives 630lbs (900-270) riding on the Expedition. 1600lbs-600lbs-630lbs = 370lbs for roof rack, kayaks, etc. Note that to make all that work I did have to be careful to make sure the kayaks I bought weren't too heavy, the roof rack was installed with the kayaks as far forward as possible, etc, etc.
If you're not big people*, I think it's likely you can make that trailer work but it will require some care and attention and trips to the scales.
*If y'all average 200lbs and you have 8 people, 200*8=1600. 1800lbs of payload** - 1600lbs = would leave 200lbs...
**Assuming you didn't get the panoramic sunroof and so have an extra 150lbs of payload