Chef's Choice makes four machines for "asian bevels," any of which would be good for your MAC. One of them, the 1520 sharpens to both 15* and 20*, and is designed for people who sharpen both Japanese and western knives. Alas, it ain't cheap. The other three (15XV, 315S, 316) will convert European knives to an Asian 15*. Whether or not your Dad's Wusties will hold the edge is another question.
The roll sharp is okay as pull-through, ceramic sharpeners go. It will leave you with a coarse, but serviceable edge at the expense of not too much effort. It will not work for the Wusthofs. It's principle benefits are that it is inexpensive and fairly easy to clean. It may be cynical, but it seems unsurprising that a representative of a knife company would recommend the knife sharpener sold by that company as the best choice for their knives.
As those things go, the best ceramic pull through for Asian knives is the Minosharp for a few bucks more.
If the choice is between a pull through and a Chef's Choice, go with one of the Chef's Choice models with a "honing" stage. It will give Mom and Dad better polished and trued edges.
No honing stage, and you'll have to add a "steel" to your sharpening set for truing the edge which tends to roll and wave, before actually wearing down. The best choice right now is the Idahone "fine" ceramic. It's an excellent hone, fine enough so as not to harm or wear your knives down, but just rough enough to keep them away from the sharpener for a long time. It's only downside is that, like other ceramic hones, it can break if you drop it. If your longest knife is less than 10" get the 10" model, if longer, get the 12". All hones require some technique and skill to use, or you risk doing more harm than good. But don't worry, it's not hard to learn.
More sharpening questions? Just ask.
Hope this helps,