What to leave on someone's grave on their birthday

Long story short, this family I know had an infant son die at birth. I visit his grave on occasion and leave him flowers, but Thursday will be the first birthday of his that I will leave him anything. I'd leave flowers on his grave, but I've already done so recently and I want to leave him something birthday-ish. Any ideas?

is there something that he's always wanted for he's birthday but never got? maybe you could leave that on his grave...or is there something he's always wanted to do for his birthday but never had the chance to do? maybe leave something that's symbolic of that.