Make sure you've got the seed words and associated passphrase for your cold storage stored (safely, permanently) somewhere he can find it when needed. I've got the seedwords in a safe, and the accompanying instructions written down in a couple places accessible by an executor.

Check out Unchained Capital, or the Bitcoin Way. I did my research following nostr:npub1rxysxnjkhrmqd3ey73dp9n5y5yvyzcs64acc9g0k2epcpwwyya4spvhnp8