Hi,
As one who lost a very close family member recently and suddenly received quite a few probate letters from local investors, my advice would be to add a good three to four sentences stating your condolences and somehow tie that in with the solution you're providing the new heirs / owners. No condelences comes off as insensitive and one sentence comes off as insincere. Three to four tells me someone has put in a caring effort.
Also, to increase your chances of success, I would call each of your leads until you speak with someone. You'll definitely stand out from those who simply send letters out hoping someone will contact them. If someone sends out a letter, but does not follow up with a phone call, that says they're uncomfortable with speaking to people about their situation in probate.
Unfortunately, for a quite individuals who will receive investor probate letters and / or calls, you will be viewed simply as a vulture preying on their grief, especially if the property they inherit is not a distressed one. For others, you may be a Godsend, depending on the situation.
Kudos to you. As an investor, I personally don't feel comfortable going after probate properties due to the emotions involved. I'm currently going through a probate process now where I've been named as an eatate administrator and emotionally, it's certainly not easy. However, it can prove fruitful for those investors that can take the heat of being labeled, plus there's decreased competition. I hope this helps.