Or maybe, what looks more legal is to have an attorney process the inheritance just like how the usual assets inherited.
and the inherited private key containing bitcoin will be stored in a bank account, so only those who have inheritance rights can actually open it.
Many other ways you can do, just choose which is the best way to pass down what we have safely.
Or simply explain it personally to someone you want to inherit your bitcoin. This will also be a good way since you can really explain and answer the upcoming questions that come up to the mind of your heir. At least you can give a clear and full explanation he/she needs.