What do I say when a relative asks my child to keep their treats secret from me?

My five-year-old whispered, "Grandpa said you'll stop our afternoons if I tell you about the sweets."

There wasn't an allergy or medical restriction involved. I had asked Dad not to give sweets before dinner. He thought the rule was fussy and told my son this was their little secret. Now my son is worrying that telling me will get Grandpa into trouble.

I can discuss a snack rule with Dad. What bothers me more is that a disagreement between adults became something a child had to conceal to preserve their time together.

[NSPCC's Talk PANTS guidance encourages children to tell a trusted adult about secrets that worry or upset them](https://www.nspcc.org.uk/advice-for-families/pants-underwear-rule/). My son did tell me. I want him to feel he made the right choice, without announcing that every surprise birthday present is now forbidden or making him responsible for policing Grandpa.

What would you say to each of them before the next afternoon? I haven't decided whether the visits need to change; I first need to know whether Dad accepts that the secrecy request stops.