Given those options, I'd go for the Expedition. Lot's of interior room in the vehicle, and capacity to tow a decent size trailer. You have to look at payload capacities, but I'm guessing the the Expedition could handle 6500 lbs. or so. But, again, you really have to crunch all the numbers, and know what kind of TT you can get by with considering two older kids, DW and yourself.
On the good side, it won't be that many more years before the kids are off to college or on their own, and you and the DW can take off and go.....if you're not college tuition poor!!!! We're past all of that and really enjoying life....writing this as we're in Wildwood, FL on our way to explore the Lake Okachobee area of Florida. Sitting out in 83 degrees beats the 30ish degrees back in Ohio!!
Good luck...hope your able to get back to the RV life!!