How to make a secure last will?

Hi, I would like to make a secure last will just to make sure that if something happens my family is able to use everything I own without getting scamed or selling something for low price. My plan is to make something like "readme" file that would contain a tutorial for dummies to everything (from managing of assets, price expectations, taxes, etc.) and save it on HW encrypted usb together with passwords, credentials, seeds, etc. Now to my question- is it save to take raspberry pi, put Tails on it, load everything manualy into the usb (raspberry wont be connected to internet during this), cypher tha usb, rewrite the raspberry. Could you spot some weakspot in this?. Usb and password will be then stored separately in family