Even if they are available and can be shipped to the door that would not resolve the trainig issue. Unforunately muzzle loaders require even more training than cartridge guns and they offer more options to make mistakes during loading. The sequence of components is important and caps not seated properly can cause failures to fire.
The blackpowder revolvers I could handle had really light and crisp triggers. For an untrained person that is begging for a negligent discharge. I would not recommend that.