The beginning of a new year is the perfect time to review and update your contacts list for your reunion invites. Every year I receive holiday greeting cards from relatives, and I typically save the return address labels from the envelopes. Then I set aside an hour or more as needed to go through them and check them against my family mailing list to update or add new information as necessary. Using a Microsoft Excel spreadsheet makes it easy to sort and manage the list.
The spreadsheet can be uploaded to Microsoft OneDrive https://www.microsoft.com/en-us/microsoft-365/onedrive/online-cloud-storage or https://www.google.com/sheets/about and shared with other family members and the reunion committee (download example spreadsheet image).
Once a year the reunion organizer sends an email asking all family members to review their contact information and either update any change of address, phone number, or email address in the shared spreadsheet. For those not comfortable working in the shared spreadsheet, the reunion organizer serves as the point person to make sure any new or updated information is promptly added so that no important correspondence about upcoming reunions is missed.