Any of this method you want to use to store this seedphrase for later use for the family, there will always be discrepancies attached to it. A lawyer is already a third party between yourself and your family, anything can happen and even the cost of keeping them can be very expensive. If you can’t trust your immediate family with your money, then you can just give the Will out before your death.
I know about that risk and not only lawyers but any entities as third party are not trusted in my opinion. I could be wrong, or I am too skeptical about third-party services but I only trust my family members. I know that are bad stories about things happen inside a family but with me, if I can not trust the people I love in my family, it's ok to let my bitcoin lost into the air and as donation to Bitcoin community.
They are your family and you know certain things that can make any method you use effective for them to access the seed phrase when you’re no more again.
I want them to inherit my Bitcoin and I will choose a right person to tell them about that, teach them about Bitcoin, wallets, how to use it (from creation, backup, recover, and transactions).
If I know how to do these things, I can teach them, just choose a right person and right time to do that.