No, they don't. If it did, you'd see an "Airbag Off" light on the dash that would illuminate when someone below the safe weight (small child) sat in that seat. The '04-up F150's have this feature. Perhaps the next generation Sport Trac will have this feature.
I first saw this in my father's Avalanche. He had just bought it and we were testing it out by sitting down and proping ourselves up while watching the air bag light go on and off in the rear view. Oh how I love discovering new things.