Separate the source appointment from the two households’ duties
Put the organizer’s confirmed details in one short message both households can use. For a music assessment, that might be “Saturday, check in at 9:20, east entrance, bring the instrument and music folder.” Then list who gets the player there and who takes responsibility afterward. Keep the original notice available so a forwarded time or unfamiliar building name can be checked against the organizer’s wording.
Confirm that both sides have the change
For a music assessment, one adult might bring the instrument while the other collects everyone at the end. If the examiner moves the time, the named contact updates both adults and waits for each to acknowledge the change. A forwarded invitation alone may never be opened.
Handle a message that reaches only one household
If the examiner calls the first household about a later finish, that household should check the exact new time and tell the collector directly. The collector replies with where and when they will meet the player. Keep the previously agreed arrangement in view until both adults know which details changed. If they disagree about the time, ask the organizer once and share the answer, rather than passing conflicting updates through the person attending.