Use the safety argument. You value your family more than you value saving a few thousand dollars a year.
Dying in an automobile accident is the leading cause of death for all Americans aged 1-34. It's the number one risk for pregnant women, it's the number one risk for your kids, it's the number one risk for you.
The NHTSA recently did research on what variables impacted survivability in side impact collisions. The safest seats were the ones in an SUV. (See "Development of a Lateral Test Procedure", slide 14, here:
http://www.nhtsa.gov/Research/Child Seat Research) In a side impact collision, the variation between the best and worst car seats in these tests were greater than the variation between the best (Britax Advocate) and worst (Diono Radian 65) car seats here: [EDIT: corrected the link]
www.nhtsa.gov/staticfiles/rulemaking/pdf/213-nprm-side_impact.pdf, p82, Figure 9.
In other words, the safety of the car you put the seat in is more important than the safety of the car seat you install (although both are important).
The reason you're paying a lot in gas in physics: it takes more fuel to accelerate a tall heavy vehicle than a lighter smaller one. But physics is also the reason the Land Cruiser is so safe. Heavier vehicles are safer in a collision than light ones because they have greater momentum. Taller vehicles keep your vital organs (head and chest) higher off the ground, and above the crush zones of other vehicles. That's why SUVs are 7 times safer than cars in head to head collisions (10 times safer if the SUV has a better crash test rating than the car does).
http://www.buffalo.edu/news/releases/2013/05/026.html
According to the IIHS, the Toyota Camry has an injury rate of 133-141% compared to the average American vehicle. While an upgrade over the Altima (especially an older Altima), it's still a sedan and will not fare well in a collision with a larger vehicle. An 03 Land Cruiser, by contrast, had an injury rate of 41% of the average American vehicle.
http://www.iihs.org/iihs/topics/insurance-loss-information
Furthermore, the driver death rate on all vehicle classes is lowest for midsize to large SUVs. Compared to a midsize sedan, the average large SUV in 2010 was about 3-4 times safer than the average midsize sedan.
The latest stats on a VW Jetta show a driver death rate of 27 compared to 46 for Camry and 13 for a GX470 (2006-2009 models). These are statistically adjusted to account for age, gender, location, and demographic factors. Latest injury results show injury rates of 110-118% (Jetta), and 133-141% (Camry).
http://www.iihs.org/iihs/topics/t/vehicle-size-and-weight/qanda#vehicle-size-and-weight
http://www.iihs.org/iihs/topics/driver-death-rates
The other thing that's interesting is that the Toyota brand is very good at making safe SUVs. All models have been "Excellent" except for the RAV4 and first gen 4WD Sequoia, which were still above average.
And it's not just about demographics (i.e. who's buying SUVs). For example, Japanese full size pickups only appeal to a certain segment of the population.
The Toyota Tundra and the Nissan Titan both look like big safe trucks, but only one was a IIHS Top Safety Pick, and only one did very well in crash testing. Drivers who chose the Toyota in 2006-2009 were among the safest drivers in America, with an adjusted driver death rate of 20 per million. Drivers who chose the Nissan were among the least safe drivers in America with an adjusted driver death rate of over 100 per million. In other words, a 2008 Toyota Tundra is 5 times safer than a 2008 Nissan Titan.
In 1999, Ford bought Volvo, the leading brand in safety innovation and research. At that time, Ford and Chevy drivers had about the same driver death rate. Safer than Mitsubishi, but nowhere near as safe as Honda or Toyota. About 5 years later, Ford began releasing new models with better crush zones. The redesigned F-150 was designed so that the engine compartment absorbed most of the energy, instead of the cabin compartment on the previous generation. As a result, the driver death rate was cut in half.
From 2005-2008, drivers of new Fords were about as safe as drivers of new Hondas and Toyotas, much safer than drivers of Chevy or Nissan.
I literally knew nothing about the 100 series when I began doing safety research on what was the safest car I could put my family in. I "discovered" the Land Cruiser by searching for a vehicle that had size, mass, build quality, stability control, and low driver death rates and injury rates.
The only thing that I know is safer than a 100 series is a 200 series, and even then not by much. If your truck control has stability control and side curtain airbags you can't put your family in something much safer.
PM me if you want more data (I have a lot!)
There's nothing you can do that helps much with the gas mileage if it's your daily driver. If mpg is the main concern, go with the Sportwagon you mentioned. My DD is an AWD Highlander Hybrid that I really like and when I drive it carefully I can get well over 30 mpg in the city; close to double what I get with L.C. And when I don't drive it carefully the HiHy is a blast because it's wicked fast off the line.
