Set timelock tnx in 2024 ( fees rates; 79sats/vb) to be executed in 2050 ( fees could be 500sats/vb), this way your coins would get stuck on the Blockchain and return to your wallet after sometime. Technically timelock can't help much.
Onchained muti-signature is still the best out there or best share your seed phrase and passphrase between two family members and leave direction of use to your lawyer. Your next of kin ( Seed phrase) your wife ( passphrase) - this way the two come in agreement to get access to the coins since they can't access the coins without the two. Seed phrase is useless without passphrase and verse versa
What kind of beta mode? About the fee, the recipient can do CPFP and that solves it. The sender should also use high amount of fee rate like at least 100 sat/vbyte. Like I have explained before but which is not yet in details, multisig also has its own downsides.
How many wallets have this features? Only electrum so yeah it's still in the beta mode and not adopted yet.
100sats/vb was not even enough to move 1 UTXO last month not to talk of in the nearest future with all the inscriptions happening on the Blockchain now. You could set the timelock and die even before you let your next of kin knows so how are they doing to know when the transactions triggers to monitor the fees?
If you're to use CPFP on $500 BTC your dad left for you at a fees of 500-1ksats/vb how much would be left in the wallet?
The best shot is to trust two separate members of the family with your seed phrase and passphrase and leave a note in a box.