May I just give a few words of caution. I have some professional experience of these matters and would point out one very dangerous pitfall if you choose to leave something of your estate to a charity, particularly where property is concerned. Do NOT bequeath a % of any property. There have been cases where relatives wished to sell a property and the charity blocked the sale, intending to hold out for a higher price. Far better that you bequeath an amount, payable upon the sale of the property, whilst not giving a share in the property title.
I haven't even read the link, but it is often said that there's no such thing as a free lunch. If a charity is offering a free will, they have a motive.