Hmm, interesting well, as you should know the key is to access the assets, and that key cant be shared if you want security. If you've lost the key or anyone doesn't have it he cant access the Bitcoins in the wallet. So you need to pass the key but there is a huge risk haha, as I had mentioned already if anyone has the key he can withdraw all the funds. More interestingly haha in reality people store Bitcoins for their hiers. I use to keep my keys mostly in a place and few of my family members know where. As you know haha Death is the reality and it can be on the head anytime.
A person who has a lot of bitcoins in his wallet and desires to transfer it to his kids when his dies would first of all know that it is not something that should be taken with leisurely. The person's kids have to be on the same page him on bitcoin and crypto related issues. The choice to reveal the key should be left to the family lawyer and there are many ways this can be achieved.
Any kid who is not should have the option of picking another asset maybe a property or business. If the man knows his kids well, this shouldn't be any issues at all.