You've responded more or less exactly the way I meant to. All I'd like to add is that, in the case of the flower garden, there is no obligation created by the fact that the request doesn't hurt anyone. You may wish to care for the flower garden, whether it's because of a choice to honor the dead person's wish, or just because you like flower gardens, but the fundamental question doesn't change just because the request harms no one. A dead person's wishes carry no obligation for the living beyond those the living choose themselves.