Thank you Cyrus3v, I will give GrowFX a shot :)
Meanwhile, anyone tried using Speed Tree? I am reading at the moment about it, it is quite pricey but they do have some Speed Tree Architect version for 400$ that seems decent, and the trees look wonderful. You can even draw your own trees with a tablet using pre-built textures and UV maps.
Not sure how would that work with Corona in the end though, probably export to max/vray then use the material converter script.