I have the GSG 1911. It works well, and seems to be quite well made for the price. When I picked it up, my FFL guy mentioned that he had also processed a Chiappa, which looked to be of lesser quality.
Is your grandson mechanically inclined? The reason I ask is because the takedown procedure on the GSG is slightly more complicated than on many 22 pistols.
Also note that the GSG has the same frame dimensions as a regular 1911, so if your grandson has small hands, he might find it a bit bulky to shoot.