I don't think that you need to deactivate the airbags for offroading. It takes a really hard hit with some damage to make them go off. Unless you are doing some extreme stuff and jumping; I wouldn't worry about it.
Actually you can deploy them with no impact at all. There's a video somewhere of a guy doing donuts in a parking lot. He switches from one direction to the next and you hear the bags deploy. As he stops, you can see they clearly fired off the side airbags, and there was no hit at all, much less a hard one.
I thought the same thing with my Sierra. Until one fateful day, a small ditch across the trail path formed by water run off deployed all curtain airbags. Not that i never beat the truck worse prior to this. Though i blame it on a sensor going faulty.
Not a faulty sensor either. Modern air bags are not controlled by those old contact sensors like they used to be.
So what's really happening?
On modern vehicles the airbags are controlled by an Airbag Control Module (ACM). This is usually bolted somewhere near the center of the vehicle. Typically it's found on/in the center tunnel between the front seats. They used to be aluminum, but some are plastic now, but they're pretty easy to identify because they're secured with 3 bolts (this assures they are mounted the correct direction).
These modules are monitoring a lot of systems. The newer the car the more stuff it's reading. Among the stuff it's monitoring is yaw, pitch, roll, speed, seatbelt usage, steering, etc. There are very complex calculations going on analyzing the data (typically in 0.1 second intervals).
The simplified version is that if the vehicle detects a Delta V that exceeds a given value over a given time, it assumes you're about to roll, have been struck in the side or have some other emergency which may result in the occupant(s) striking the side windows, pillars, etc. To prevent possible injury the side curtain airbags will deploy.
It's not a defective sensor because multiple sensors are feeding data to the system, nor is it required to be an impact. It's just a matter of what the vehicle is doing, and the potential implications that movement means to the occupants. The only way to prevent a deployment is to disable the system. Either cut power to it via the fuse, or unplug the harness altogether. And unplugging is not easy because they're often under the carpet, or console, etc. They're intentionally not out in the open where they'd be easy to get to.