lots of gorges and canyons and I would like to fly over to get some video.
Don't do that.
Tello has only a small range about 100m. Except you take a Wifi range extender. But that would not be enough for your intention.
Also VPS will fail. That works only up to 30m.
And the Tello has a maximum speed of 30 km/h. That meens, if you have a wind with a speed of 30 km/h you only can try to hover. No chance to fly, e.g. to come home. And when the wind speed is above 30 km/h the Tello follows the wind. And you will lose her. In the canyons you often have a strong wind.