I currently have a 05' Chevy Suburban & a 11' Ford Fiesta. We have 4 children & 2 dogs & love the outdoors. The Suburban is great & does it all but good gas mileage (16 mpg) & the Fiesta will not fit family but gets great mileage (40 mpg). The Fiesta will fit 5 adults (tightly) & actually has a good amount of space in rear hatch but not enough for dogs.
There will little to no fuel savings going to the Tahoe over Suburban but will loose a bit of room inside. The Ford Expedition is very similar to the Tahoe.
We had the Toyota Sienna & will never go back after the Suburban, the minivan is just to limited.
Hope this helps