I agree. TPG's are what I choose. They remove questions about authenticity, grade, and identification. The last can be particularly important for tokens or non-US coins. Important other facts can be added to the back of the slab with a label-maker. In this way, I think my heirs will at least have a fighting chance of not getting pennies on the dollar. I like the idea of communicating suggested auction houses or dealers. I intend to add that to the "fill in the blank" page of my will ASAP.
To those who plan to sell before you pass, I agree that this would be ideal. The question then becomes: When? As one who has unexpectantly woken up three times in intensive care and being told once that I may be permanently blind, once that I would not survive the night, and another that I would not survive 48 hours and to get my affairs in order, I can assure you there was not a lot I could do semi-conscious in an ICU bed with various parts of me not functioning.
Even today after cancer, stroke, numerous surgeries, stiches, staples, glue, clips, cauterizing, plates, rods, screws, and significant ongoing organ damage with a poor prognosis, I don't want to sell off everything. It feels like I'd be throwing in the towel and waiting around to die. Plus I enjoy coin collecting more now than ever.