In my opinion, you can just suggest and say your peace. What your son does with it is the learning experience.
I am 35, an only child, with no remaining parents or grandparents and I have handled each loss with a different reaction based on my growth and/or (sadly) numbness to death at this point in my life. Both of my grandfathers passed and I was too young to get it. My father's passing was expected and we were blessed for the extra 4.5 years of time packed with lessons I got with him. I still have "you dumb son of a bitch, this is what he meant" moments. His mother was so far gone with Alzheimer's and dementia, I was just glad it was over and but sad that I am sure she died not knowing her son was dead already. That is a long story for another day. My mother's passing was so sudden I just went into "go" mode and started getting things handled. It was a gargantuan task, but all I could do was move forward. I am just blessed that I had already met my wife and she understands my numbness to it all and how I handled it. Then my mom's mother expectedly passed a couple of months later. I was so caught up in handling what was already on my plate, I just went about my business and it really didn't affect me. I am still sad, as that is the person I was closest with besides my parents, but I was more at ease as she had become a different person. I'll never remember her as she was in her final months, but as the woman I grew up with every summer.
There is no right or wrong way to handle it. Just push him in a certain direction that you, in your core, feel is right and the rest is something he will learn and grow from.