d. seltzzer: “obviously you didn't read the specs. you can mount either left or right. “

Obviously, you didn't read the post or any of the comments. Left or right, it matters not, the criticisms still apply.

d. seltzzer: “also you are lucky not to have a progressive disese that makes it imposable to grip the slide. “

I do feel fortunate. I do not work with disabled shooters, and as has been mentioned ad nauseam, this is not a recreational shooting blog.
Someone who has no ability to grip the slide probably also lacks the strength to hold on to the weapon during recoil without causing a malfunction.
There will eventually come a time when, despite your best efforts, you are just not capable of fighting anymore.

d. seltzzer:“…glocks have a history of slam firing…”

Even if that was true, which it is not, I am not sure what that claim has to do with charging handles.
You might want to remove your finger from the trigger before you rack the slide. That might solve your “slam fire” problem.

d. seltzzer: “…and using the sight is quick way to injure yourself or others”

Amazingly, despite many iterations during practice, I have never been injured, nor has anyone else I know. Are you sure you are doing it correctly?
Also, the original purpose of the technique is to rack the slide in case you are already injured, e.g. shot in the other hand. The chance of injury is infinitesimally small and the severity of the potential injury is absurdly trivial, comparatively speaking.

d. seltzzer: “…in the business since 1972”

The business of selling charging handles, no doubt.

By mounting this gadget on the pistol, you have actually increased the possibility of a malfunction. This is just a mechanical fact. Ironically, you now have created an increased likelihood for an emergency requirement to manipulate the slide because you wanted to make it easier to manipulate the slide. Making something easier does not always make it better.

If the pistol is for defensive use, and this device is mounted on it, then you really owe it to your father to ensure that he practice malfunction drills above and beyond what would normally be required. Or you could get rid of the handle and train him to overcome his disability. Either way he is going to need to train with the handgun. You could also suggest he try a firearm that is not as difficult for him to manipulate. You may also want to read Mostly Genius' post: Firearms for the physically disabled.

Finally, 6 year olds should not be operating pistols (or any other firearm) without adult supervision. I am not sure I want to make it EASIER for children to manipulate handguns.