Unfortunately, I would suggest that there is no way they aren't going to be overloaded. As capable as the X is, the GVWR usually leaves a cargo capacity more akin to a regular 1/2 ton SUV. That trailer, alone, is likely to use the entire available payload of the X before you consider passengers and gear in the truck.
Now, there are MANY Excursion owners who argue that the rating of the X is very low, and that you are ok to exceed it. That is a decision your friends will need to make for themselves. Hoping to stay within ratings within that set-up, however, is pret unlikely.
