What is the load index of your current 22 inch tires?
Tire Load Index Chart | Tire Load Range Index | Discount Tire
How about the ply rating, or load range? Assuming they are P tires, and the reason I ask is a lot (but not all) 22's are low profile, and many (but not all) lower profile tires have a light load range. --LL on the sidewall-- If you are unsure, its worth looking into.
Tire Tech Information - Load Range / Ply Rating Identification
You'll have to do some math to determine weights in order to tell if your current tires are suitable or not. Your truck, your passengers, their cargo, and your trailer weight & tongue weight will all have to be taken into consideration. Aluminum or fiberglass 20' trailers can be extremely light, while others can be ridiculously heavy.
There are PLENTY of 22 inch tires that are not suited for an Expedition, let alone an Expedition pulling a trailer. Not suggesting you run out and buy 10 ply LT tires, just encouraging you to evaluate what you have.
The bottom of the second link has info on trailer tire ratings, so you can also determine if those are appropriate or not.