To me, dying at 84 is not a "surprise" or "tragic", it's "winning the game".
The average life expectancy in the US (as of 2011) is 78.64. For women, it's 81. As far as I'm concerned, if you beat the average, you've done well.
Anyway, I wish you luck on getting it all straightened out with the family. I see what you're saying about there never being a good time, so it's "always" a good time.
Luckily I've never had major grievances to deal with in my family, so I'm probably not the best at giving advice for this. But I think your feelings on the matter should probably guide the way. That is, if you feel it's important to have it acknowledged, then by all means, do what you can to get it out and the open and talk it out.
My feeling is that old wounds will continue to fester. It's best to discuss things as soon as possible, otherwise you just build resentment that grows with time.
One possible counter-argument however is that some people are incapable of admitting their contribution to a problem, or will never change their behavior. In such cases, you have to decide how much you want them to remain in your life, and whether sweeping things under the rug is sufficiently justified.