Go to the funeral, if it happens. Stay in a motel, not with family. Be courteous and polite, but not intimate -- you left long ago. When asked why you're in a motel, reply "Because I didn't want to trouble anyone" (which is completely true). If someone brings up the past, pass it off with a kind word and keep your thoughts to yourself. Don't involve yourself with hate and despair.

"Do you know that in 1947 he called my mother a gross fat pig eating slops???"
"Really?"
"You didn't know that?"
"Why, no."   

Don't point out that whoever "he" was/is was three years old. Feign polite interest in a story you've heard a thousand times and quietly leave as soon as you can. Don't take sides -- they're all probably in the wrong.

As a daughter you might be in line for some inheritance. Pay for a decent lawyer and let the lawyer handle things, and you refer everything to the lawyer (that's why you're paying a lawyer). If asked why you politely say "I wanted to be certain everyone and everything was done right." Don't fight the will (if any) but don't fold up like a cheap chair, either. The lawyer's fees will be worth the lack of hassle you'll have, and I know about that.

What has happened is past. Don't let it carry into the future. If they never speak to you again, so be it, but they are probably aware of situation and may be trying to "make the most" of it in whatever way best suits them.