I think anything larger will definitely cut in to your mpg.... the 23/24 is that around town? highway? If its around town that is really good for a V6 anything!
I have a Sienna - and running the AC at full blast i only get 16/17 around town..... yeah it stinks considering i used to drive an Altima, but well it cannot be beat in terms of convenience.
My MIL has an Escape - which is basically the Ford version of what you are driving and her mileage is very similar. So i would expect any mid size SUV to be about the same.
Honestly the only large SUV that i would think about driving is a Honda Pilot, which has top tethers galore but as with every 3rd row option SUV i have ever seen when you put that third row up you have little to no cargo area.
It sounds like for your needs a newer model Oddysey or Sienna might work. My neighbor has a 2007 Oddy and gets 19 mpg around town with it. The sienna just has a LOT of glass and if you look at how much it weighs it actually is only a few hundred pounds shy of an extended cab pick up truck in terms of the weight of it!
And it only has a v6 pulling it around which most trucks will have a v8 with more power. My friend has a brand new 2011 Oddy and gets about 21mpg around town.... she loves it. The gas mileage alone makes me want to trade up! Lol... but alas mine is paid off and i detest car payments so i will keep mine and just walk more, drive less
Good luck on your search!