Heh, okay I guess what I wanted was going to end up as the worst of both— fixed amounts off the top to some particular people/causes, and then the remainder divided into shares for my kids.

I guess there's an understanding the being an executor is a best-effort role, but maybe you could specifically codify that +/-5% on the individual shares is fine, just to take off some of the burden of needing it to be perfect, particularly if there are payouts occurring at different times and therefore some NPV stuff going on.