First, be careful: old people are easily startled and can behave unpredictably

Offer him a warm bowl of Metamucil, and invite him to share stories of how little things cost in the past compared to today

When he is warmed up, that's the time to reveal that there is an anonymous world benefactor with a Japanese pseudonym who is bent on replacing all the worlds gold and cash with virtual digital tokens you must have an Internet capable computer to utilize

Btw keep emergency services and a defibrillator on standby