Hello Pete,
Nice one !! Mother Nature provided the material and is at liberty to do with it as she wishes, irrespective of any ideas which we may have !! Going with the hand sanding is always preferable if a little more time consuming. That way we retain better control of the outcome, especially around the live/natural edge. The cracks are a part of the life of the piece and many potential customers will buy into that !! You may also find that treating cracks takes an inordinate amount of time which potential customers may be unwilling to buy into !!
ATB John