Wow good question. I think you're missing one big point, in that I'd want it to relate them to me, and who I was, what it was like when I lived, etc. So in that sense I'd definitely leave a video of myself explaining, maybe a tour of my place, my city, transportation, etc. A video collage.
Next I'm thinking if I were to get something from an ancestor right now, what would I want? I think maybe an assortment of interesting unique stuff would be cool to have. The coins are a great idea because they'll easily last. Maybe some beatles memoribilia? A few magazines... golf ball?
Just little stuff we consider normal that might not be so normal in 200 years.
As to high value old things, I'd inquire with an antique expert who would understand better the way things age, and what would be valuable.