Those smaller activities like planting and taking care of trees can be handed over to subordinates.
But for something like leveling out an entire mountain, unless there's some enormously powerful explosives to help, it's unlikely the work could be finished within a few years—or even decades—if left to others.
Even though giant dragons have extraordinarily long lifespans, spanning thousands of years, such a long time is enough for a baby dragon to grow into a young adult dragon. To a giant dragon, that's still not an insignificant period. Besides, Leon, who has a human soul inside him, is seen as overly impatient by Tassera and Cecilia. He simply has no patience to wait that long.
"If only we had some nitroglycerin."
