He also said that in the long run we are all dead so I'm not sure I'd trust him to have the best interests of our 'grandchildren' at heart.
Well he’s not wrong. We’re all dead at the end.
What is your impression of mortality?
Do you honestly believe that he meant it in a literal sense? You as well as I know that he meant it would be better to emphasize on short term plans as opposed to long term plans. It is simply a question of time preference and I'm simply saying that he would therefore not be best placed to make plans for our grandchildren. He'd be inclined optimize for the present as opposed to the future especially when we're resource constrained as we often are.
Do you honestly believe Keynes' point with this pithy aphorism was that short-term plans are always superior to long-term plans? The fuller quote is "But this long run is a misleading guide to current affairs. In the long run we are all dead. Economists set themselves too easy, too useless a task, if in tempestuous seasons they can only tell us, that when the storm is long past, the ocean is flat again.". He was pushing back on the use of a theory of long-term economic equilibrium in predicting day-to-day conditions, not expressing a preference to screw one's grandchildren over for present gains.