This is very sad for you both Rio and I'm sending heartfelt condolences to you. Did the therapist offer any advice about helping your grandson? I think that the more we can bring ourselves to talk about a loss, as in deceased loved one or pet, it keeps them alive in our hearts. Share pictures and happy memories with your grandson as frequently as you can without being maudlin or too whistful. Introduce him, with owner's permission, to other dogs when you're out with him and if it's the right time or thing to do, when the time of mourning is less acute, maybe rescue a dog and involve your dear grandson in the process of choice. My heart goes out to you both but it's only right to mourn your GSd out of respect for the joy your dear doggy brought to your family. I hope your young one will soon feel better and more relaxed. Hugs to him and you.