I can speak to that from a somewhat personal perspective because I lost my older brother a few years ago, which means I got to witness my mom losing a child.
I know that she would have greatly appreciated simple flowers later after his passing. She got a lot of flowers and stuff when he passed, which made her feel like he was very loved by his friends.
But then a year later, only a few people remembered. And I think that’s what hurt her the most after the obvious pain of losing her son. That people forgot.
So if you knew his son, you can write a card about how you still remember him and add flowers to that.
It’s usually not about the actual thing you give him but how it’s presented and the words that go with it.
P.S. you are a good person.