So, say 50, 100 or 200 years after my passing, and the terms of my will have now been forgotten. Who or what would prevent disposal of the said property out of the family (against my wishes)?     in a will you   “entrust” to a trustee the performance of your wishes.. if your trustee is untrustworthy then who exactly will be around to fix it.?

The million dollar question.. perhaps make the trustee a reputable accounting / legal firm?    Usually thats the case.. its’ one of the reasons firms advertise their date of inception..eg  since 1884  or est 1925