I found a property, how do I approach the owner?

[Brenda E.]

I found an abandoned property - like abandoned for 75 years.  I did my research: the owner was dead. I found his widow, who, at 92, was living in another county with one of her children.  I knew the family must know about the property, as the taxes has been paid. I wrote a letter asking if she would be interested in selling the property.  I did not hear from her, so I wrote to her again a year later.  I still heard nothing from them, so I figured they didn't want to sell.  Another year later, I checked the status of the property again, and to my surprise, they sold it to a developer literally 2 weeks before I checked on it again!  The amount was what I would have paid, but they never contacted me. 

I found another property of  similar status (abandoned for about 50 years).  The same thing happened.

Now I found another one - I have told no one where it is. It has been abandoned for 50+ years; owned by the owner for 100+ years. The owner is dead; his wife is dead; the real estate taxes go to their daughter who is 70+ years old and lives in another county.  I don't want to lose this property, so what do I write, or what should I do to make an offer and make sure my offer isn't disregarded.  Do I send it certified? Do I give a sob story? Do I have a lawyer write it? Do I put an amount in the letter? Do I justify the offer? Do I offer to pay for their lawyer or offer to do the title search for them so it'll cost them nothing?  

What should I do???  Thank you anyone for your help!