If you can't explain bitcoin to him, then you can't dishonor his wishes either.

You can refuse the terms of the gift, or ask him to help you set it up, or you can suggest a different arrangement that gives you the freedom to store it however you feel is suitable.

Ultimately, his "gift" has strings. Imagine you gift his kids Bitcoin, but he's gotta set up and look after the wallet for them and if he did it wrong, it's his fault not yours. Would he feel comfortable with that arrangement?

Imagine I gift your kids $1M in pennies. Should you be grateful and find a way to store it all safely for the kids despite you not having anywhere to keep it, or can you politely request a different form of gift and it shouldn't be controversial.