chevrolet makes a tahoe and a chevy suburban, GMC also makes a suburban the SLT model has all the power options and is a much nicer version of the suburban, chevy suburban is more bare bones, gmc makes a vehicle similar to the tahoe, but is called something different.
The difference between the suburban and tahoe is 18 inches taken out of the middle of the suburban. It is roughly 1,000 lbs less, and the 18 inches is more or less the cargo room behind the rear seats. I have had suburbans for years, I liked the extra 18 inches, it made all the difference in the world when traveling long distance with four adults and several kids, but if you do not need the extra room, don't get it, extra weight decreases the gas mileage.
the newer suburbans or tahoe has a 5.3 liter v8, this is a great engine, and a two wheel drive the mileage would be decent enough, and the fuel injection but with any large vehicle, gas mileage is an issue,
A two wheel drive suburban is better on gas, than the 4x4, honestly, if gas mileage is an issue, I believe there are many other vehicles that can do the same job for a lot more miles per gallon, from the safety standpoint, suburbans and tahoes are large and heavy, sturdy and strong, and will take a beating and drive home, but the same thing that makes them a sturdy vehicle is the same thing that eats all the gas.
the two wheel drive version would be better on fuel, than a 4x4
You may want to consider a nissan, or if all wheel drive is needed, go with a subaru, subaru has been doing all wheel drives since the beginning, and they have a 4 cylinder boxer engine and tranny that has been a proven winner for strength and durability. Honda, makes some really good cars too, so it all depends on what works for you guys.