I would also double outer box too, just to be safe. Most damage (other than unavoidable catastrophic stuff like a forklift prong straight through something) occurs with penetration of the exterior box, an inner sacrificial box helps avoid that.
I package like this, if the toy box isn't sealed, I usually fill the voids around the toy with packing peanuts to avoid movement of the item within the toy box. This is then bubble wrapped with two layers, carefully, avoiding tape anywhere near the toy box. This then gets placed in a shipping box with around 4 or 5 inches all the way around it filled with packing material (air pillows and peanuts). This box is then taped up, bubble wrapped and placed inside a slightly larger box with around an inch or so of packing peanuts, then thoroughly tape up the outer box. I apply two or three destination labels around the outer box in case one gets defaced, and I go over all these with sellotape to protect them.
That's pretty much the best you can do to protect against normal shipping wear. If it gets damaged beyond that, then nothing would have saved it outside of a wooden packing crate....
cheers,
Andy