I'd share videos and links, a complete package, OR leave it as part of inheritance with a family lawyer. There are technical means to also achieve this that are more trustless but for now, when most people don't know how to use Bitcoin, might be best to stick to understood methods:)
Making video instruction is a good idea but technology is developing so quickly and it may not be so easy for people in future to play this video.
Imagine recording video with betamax, vhs cassette or even CD not so long ago, and now it would be very hard to play some of them.
I still think that writing instructions on hard paper is better, but you can add optional audio-video recording.