Our kid's cards were all conditionally approved on renewal (before the expiry date on the cards). I saw vague wording on the Nexus portal that expiration would be extended but it wasn't clear how long for (I think I saw posts mentioning 2 years, but wanted to confirm).

Do we need to travel with the conditional approval letter once their card expiry passes but before the (1 yr? 2 yr?) grace period passes? or are we fine to scan at the border the expired cards and it will just show as valid on their end?