they'll recover... eventually. it might take them years, but they will recover from your death.
apart from anything you put in your suicide note, there isn't much else you can do, sadly. i'm in the same boat as you, except i "came to terms with it" when i was like 14 (four years ago) and feel that my death is priority over their sadness. that doesn't stop me from feeling slightly guilty, of course, but it's not something that'll stop me when the time comes.
but... yeah, i get you. a lot of users here think that their family will forget them, and maybe that's true, but it's equally likely that their family will remember, and even 40 or 50 years into the future, the death could still be a sensitive topic in their hearts.
all you can really do is accept that, and weigh if you are okay with doing that to them.