Need advise to find the ultimate solution to protect my BTC with a multi-sig wallet

Hi,

Today I use a 24-words wallet generated by a hardware wallet. The secret words are stored in a physical vault, in a bank. The issue with that, the bank could force the vault in case I am considered as a problematic person, or simply if I die. This could be problematic to transfer the funds to my kids safely. If I die, an intermediary will be in possession of my seeds before they are transferred to my kids. Other issue, someone could use the same 24 words (I know, out of 2^256 possibilities, it is virtually impossible).

I thought that a 2-of-3 multisig wallet could solve my problem but I struggle to find safe solution for the very long term in the scenario where the app that created the multisig wallet does not exist anymore and where my computer is not accessible.

To get familiar with multisig, I created a 2-of-2 wallet using Specter, with two 12-words paper wallets. I exported the wallet using the format for Electrum. Then I imported the file with Electrum. Then I was able to generate transactions without any other key, signature or anything. The export file was enough to authorise transactions. I find this even wore anything else.

How can my kids have access to the funds, if I die and if they have only 2 out of the 3 keys without compromising the security of the solution with a file export that could be used by a malicious person?

Could you help me to understand?

Thank you